Honestly, in my mind it only ever means to ask someone to marry you. Perhaps people use that original meaning to suggest shyness about asking another question, "have you, 'popped' the question about if she's going to leave work or not??". Meaning it's a moment of worry, maybe even could be sarcasm, as though you were supposed to be scared of someone but you weren't, "so did you pop the question to Lynn about her leaving work or not?", But to me it means did you ask him/her to marry you.

1. to ask someone to marry you; - I remember he popped the question while we were eating ice cream. 2. to ask about something that is very important; - So then I pop the question, When do you expect this to happen? So, sure sometimes it means to propose and may be you surprise somebody by this proposal. :D ;) Good Luck ;)

Understand it as not "pop the question", but "pop THE question". THE question is the question of marriage. It only means that. "Pop A question" means to surprise someone.

pop the question = to suddenly ask any question of extreme importance It is mostly used though to mean "marry".

To Surprise some1 with a question, unexpected by the other person. specially like a marriage proposal