I think that's also the more "technical" term for armpit in english, so probably not an accident: https://en.wikipedia.org/wiki/Axilla

Yep, comes from Latin! [1]

[1]: https://www.merriam-webster.com/dictionary/axilla#:~:text=Th....

In Spanish too. The usual term it's "sobaco" which came from sub-brachium, under the arm.

Didn't know that! In Portuguese, we use the word "Suvaco"