Steer is Germanic (German has "der Stier") but heifer is unknown origins.
It does sound similar to Hufer (e.g. as in Paarhufer, literally sth like 'paired hoofers'), but the Wiktionary states it's indeed of different origin. Etymology is really fascinating sometimes
Their origin, I mean. I can google, but it's more fun to hear what others have to say. And argue, and put them down and up - or try to :)
Attitude frowned on by HN, I know, only they don't (seem to) know they are doing it themselves, via the voting mechanism, i.e. upvotes and downvotes.
Also, it's interesting that there are so many words for horses in English and Western (cowboy slang, I just made up the word :)