off = wy-

on = w-

Yeah, they're very problematic in pronunciation, sometimes you really need to stress the beginning of the word.

Well, if the light is off, then most probably you're asked to turn it on. And vice versa. So usually you wouldn't be confused.

OK, added now.

A new thing learned... added.

Turning the wick of the paraffin lamp lower. An blow it out.