>     For the first application, we use "Right" in the sense of right = true
>     = correct = ok.

That's clever. I had never noticed the intentional pun.

> In this case, Ok/Err would also be ok (another pun not intended).
>
> Indeed, the ambiguity between the meanings 'opposite of left' and
> 'straight, correct' goes back to Proto-Indo-European six thousand years
> ago.

Pretty wild.

> I was going to say that Lassi, who speaks a Uralic language, is
> excused from noticing this pun, but it seems that Finnish _suora_ has
> both meanings too, probably because its root is borrowed from Common
> Germanic _sta-_ 'stand'.  In Hungarian (very distantly related to
> Finnish) they are utterly different.

The Finnish words for left and right are "vasen" and "oikea". Like its
English counterpart, "oikea" shares the connotation of "correct": "oikea
vastaus" is both literally and figuratively equivalent to "the right
answer". "Suora" means "straight" (as in a straight line). It is a
literal word only and does not have figurative connotations such as
"correct". However, the inflection "suoraan" means "directly" and is
used semi-figuratively to say that something is accomplished in the
easiest or fastest way.

I don't know any Hungarian, sadly.

> At least English uses "Go straight!" and "Go right!" as unambiguous
> driving directions.

This is the case (no pun intended) here as well. "Mene suoraan" (go
straight) and "käänny oikealle" (turn right).