Broken Shells Make Temple bells' meaning?

Question

There is a great Irish song 'As I Rover Out'. The 'Omnia' band made a remake of this song called 'Who Are You?'The meaning of the certain sentence in this remake became a subject of discussion between my collegue and me. Could you please kindly clarify this enigma?Let me citate the context lines:"*When can I return again and when will we get married?* ***When broken shells make temple bells,*** *that's when we'll be married.*"My colleague thinks it means *'when broken shells turn into, become the temple bells'*, though I think it means *'when broken shells make ringing the bell of the temple'*.Which opinion is true? Or, maybe, they are equally correct?Thank you in advance for the answer!

Answer 1

According to irishmusicdaily.com:

The song ends with the soldier/sailor abandoning the girl he's slept with. She asks him when he will return and marry her. He replies "When broken shells make Christmas bells"...in other words, never. Similar to, "when pigs fly."