Dexy's Midnight Runners. Always heard "come on Eileen oh I swear unto thee" as "oh you swear on TV". Because nobody ever swore on TV, so that would be an outrageous thing to do.
A childhood belief about misheard lyrics

others believed things like this
- I swear I heard a Disney Channel/Radio Disney song where the chorus was a repeated “Damn it”— SpengBab
- CCR's Bad moon on the Rise, I swear it sounded liket they were singing, "There's a bathroom on the Right"— SMC
- i could swear eleventeen was a number for the longest time -- it still sounds pretty convincing.— erin
- i used to belive that if you swore you would be arrested— kd
- my mum told me when i was 11 if i swore the police would take me to jail. — tg in blue
- I was told that if your ever swore in church, as you walked out God would strike you with a bolt of lightning.— Lou