I didn't have this idea, but some of my friends did. I'm Polish and for Holy Communion we learnt a hymn that ends with words "Jemu chwala i czesc" which means "Glory to Him and honor (to Him)". But in slang, especially kids slang but not only, "i czesc" means also end of discussion, kind of like saying "period." at the end of sentence. My friends thought the hymn meant "Glory to Him, period."
A childhood belief about hymns

others believed things like this
- For whatever reason, I thought that grass was slang for tobacco rather than marijuana.Anon
- I used to think Cockneys only ever talked in rhyming slang.Anon
- "Chassis" is slang for a woman's body, especially her genitalia.
— Siddharth Mehrotra - i used to think the word "friendship" meant a special kind of rocketship that you went on with your friends.— chips ahoy!
- I used to believe God had a pet tortoise. There was a hymn we sang that went "Great things he hath taught us"— Lozza
- When he was a kid, my husband thought the hymn "bringing in the sheaves" was "bringing in the cheese."Anon