if he didn't have to learn the language, then doesn't that mean he has an auto-translate type gift, so wouldn't it convert the name to the proper earth name?
Exactly. Which is why media for present-time human consumption is rendered in present-time human languages. Yes, they could be speaking Aramaic, Klingon, or Scouse, but "onion" is till going to be the target-audience term for a thing that largely looks, grows, tastes, and is used like some onion we know. Now, if that onion grows in the crotch region of a klipklop, tastes like strawberry, comes in the shape of a starfish, and is liquid inside so that you harvest it like squeezing a pimple, then you can start making up names. Until then: onion. Everything else is just rename-wank for rename-wank's sake.