• When it comes to English the problem can be split into two: the origin of the word, and its usage to refer to the planet.

    The origin of the word is actually well known - English “earth” comes from Proto-Germanic *erþō “ground, soil”, that in turn comes from Proto-Indo-European *h₁ér-teh₂. That *h₁ér- root pops up in plenty words referring to soil and land in IE languages; while that *-teh₂ nouns for states of being, so odds are that the word ultimately meant “the bare soil” or similar.

    Now, the usage of the word for the planet gets trickier, since this metaphor - the whole/planet by the part/soil - pops up all the time. Even for non-Indo-European languages like:

    • Basque - “Lurra” Earth is simply “lur” soil with a determiner
    • Tatar - “Zemin” Earth, planet vs. “zemin” earth, soil
    • Greenlandic - “nuna” for both

    The furthest from that that I’ve seen was Nahuatl calling the planet “tlalticpactl” over the land - but even then that “tlal[li]” at the start is land, soil.

    The metaphor is so popular, but so popular, that it becomes hard to track where it originated - because it likely originated multiple times. I wouldn’t be surprised for example if English simply inherited it “as is”, as German “Erde” behaves the same. The same applies to the Romance languages with Latin “Terra”, they simply inherited the word with the double meaning and called it a day.

    And as to why Earth has become the accepted term rather than ‘terra’, ‘orbis’ or some variant on ‘mundus’, well, that’s a tougher question to answer.

    In English it’s simply because “Earth” is its native word. Other languages typically don’t use this word.

      • That ⟨地球⟩ is perhaps the only exception that we’re damn sure on how Earth got its name. The guy who coined the expression was a priest of the Papal States called Matteo Ricci, living in Ming around 1600. He did a living translating works back and forth between Chinese and Latin, and calqued that expression from Latin orbis terrarum - roughly “the globe of soils”, or “the ball of earths”.

    • Late because I only discovered it first now but this is quite interesting. When I first read this post my initial thought was also to investigate Basque and other language isolates, but by coincidence I just happened to stumble upon the Ainu (language isolate (according to popular consensus from what i can gather anyways) that’s native to Hokkaido and parts of the easternmost islands of Russia) word for The Earth while looking through wiktionary: aynumosir (アィヌモシㇼ) which roughly means “the land of the humans.” Compared to the Nahuatl example it also seems that the word for “land” (mosir (モシㇼ)) does not have much to do with the word for dirt/soil on its own and seems to more explicitly refer to land as in territory/country, meanwhile the word for dirt/soil would be “toy” (トィ). As far as I know this would be the word for The Earth that is the furthest removed from having with earth/soil to do. Additional fun fact is that the Ainu word for the equivalent of heaven is “kamuymosir” (カムイモシㇼ ) which roughly means “divine territory/country.”

      • That’s indeed really far from the “dirt” → “our planet” connection.

        I dug a bit further into this matter and perhaps Ainu is not an exception. Perhaps - please take what I say with scepticism; I’m just hypothesising, nothing solid.

        Accordingly to this Ainu-English dictionary, the word sir / シリ on its own means

        1. weather, appearance, status, condition
        2. land, island
        3. mountain

        Meanings #2 and #3 might be the result of simple homophony, but I think that they’re related. And that the word モシㇼ/mosir is bimorphemic, with the second morpheme being “that” シㇼ/sir, that originally meant “soil” - otherwise it’s hard to explain how it evolved into “mountain” under meaning #3. With then トィ/toy displacing the “old” word, and becoming the main word for “dirt, mud, soil”.

        Or perhaps it’s just an exception and my hypothesis is bullshit. Either way thank you for bringing this piece of info up.

        • Interesting hypothesis! It’s indeed likely this could be the case, it’s just unfortunate only one variant of Ainu remains and that it’s in quite a precarious position, but it’s fun to see different paths of how words picked up their meanings either way.

  • Yes we do know, It comes from the Latin language during the roman empire. Terra which means soil/ground in Latin. it deviated to Terra in italian and portuguese, tierra in spanish and terre in french.

    English was influenced by french so they took the meaning of earth from there. The word earth in english comes from old english or irish I dont remember correctly.

        • It’s the opposite - the name of the primal goddess is just the word for ground. The same things happens with other gods like Hestia (hearth), they were named after the things that they personified.

            • We can’t be completely sure of that, as it’s based on inductive reasoning, and indirect evidence. …but nor I can be completely sure either if my lunch will be actual chicken or if the butcher sold me Cthulhu’s flesh shaped like chicken tights. So eventually we need to draw the line and say “nah, we know this well enough”.

              And in the case of Γαῖα / Gaîa, the presence of a coordinated term γῆ / gê “land, earth, soil” (NOM.PL γ(έ)αι /g(é)ai ) is strong indicative that the god was named after the concept, not the opposite. That word pops up all the time in compounds, even for mundane things like γεωργός / geōrgos “farmer” or γεωμετρία / geōmetríā “land measuring → geometry”.

              It also fits rather well how epithets are assigned to gods, and often evolve into names themselves.

              Now, if the word is from PIE *dʰéǵʰōm “earth” or some Pre-Greek substrate is another can of worms, that is far more dubious. The presence of forms like Δᾶ / Dâ hint me the later; possibly the original language used something like *ɟea, and different Greek dialects adapted that */ɟ/ into /d/ or /g/. Curiously the forms that pop up in compounds for other nouns use /d/, like Demeter (“mother De”).

              • The most fascinating part about all this is that the Greek culture goes as far back as the last ice age where the Greek genesis myth references things that could potentially refer to those geographic circumstances. There were also a lot of invasions and colonization of that area and the new people tended go absorb some of the culture from the defeated ones which is where some of those names come from. Like it’s fascinating that Gaia is a pretty important goddess, but wasn’t really honored and mentioned as much as the dodecatheon and neither was Uranus. Almost like deist entities.

                I’ve read people suggest that some of these almost prehistoric names come out of onomatopoeia. What do you think?

                • It’s beautiful, isn’t it? We look at the past, and it opens a small window to an even earlier past.

                  It’s a bit off-topic but here’s another example that I find also fascinating - horses in the Greek myths. What’s up with the divine twins Castor and Pollux being always pictured with horses? Or Poseidon, a sea god, creating land animals? Or the association between horses and glory in battle?

                  Sure, horses are useful, but less so in a rough terrain; and the Greeks weren’t exactly mass breeding horses, they were mostly a resource for rich people. Almost like they inherited some myths that only made sense in another environment full of open fields, where horses were a way of life.

                  And just like the genesis myths talk about what happened from the PoV of the natives, those horse myths talk about the origin of the invaders, as steppe nomads near the Pontic Sea. And then suddenly you find a lot other similar myths, in other Indo-European cultures; such as the Rigveda with the अश्विनः / Aśvinaḥ (“horse possessors”, divine twins, who save people from the sea), or Germanic tales about the sea invasion of Britannia being led by Hengist (stallion) and Horsa (horse).

                  It makes me feel like everything is connected, and perhaps we shouldn’t be even talking about “Greek culture”, but just that Greek portrait of human culture.

                  But I digress. (Sorry, I tend to talk a lot about Indo-European culture, it’s one of my passions.)

                  I’ve read people suggest that some of these almost prehistoric names come out of onomatopoeia. What do you think?

                  Personally I find it possible but unlikely. I think that they get those short, almost “bah!”-like forms due to erosion, caused by sound changes and the borrowing process.

                  It’s simply that we don’t know enough about its etymology further back to “see” a well-structured word. All that we see is that “gê”, sometimes “da”.

                  Like it’s fascinating that Gaia is a pretty important goddess, but wasn’t really honored and mentioned as much as the dodecatheon and neither was Uranus. Almost like deist entities.

                  Yup! She’s a goddess, but she lacks all the whistles and bells that you’d associate with the Olympians, because she’s more like a divine aspect of nature. By worshipping her you aren’t just worshipping some abstract entity in the middle of nowhere, you’re worshipping the very soil that gives you sustenance.

                  It’s interesting that you mentioned Ouranos, as it’s another god with a rather transparent name: οὐρανός/ouranós is the sky vault, where the stars are attached to. Your association is spot on - he’s also a divine aspect of nature, a step further from humankind than the Olympians.