I thought the line "round yon virgin" in Silent Night was supposed to be "round young virgin" (I wasn't sure what a virgin was, but I knew it meant Mary). I thought it was a commentary on Mary's post-pregnancy body, kind of like a polite way of saying she was fat.
A childhood belief about misheard lyrics

others believed things like this
- I thought "Virgin Mary" was actually "Verge 'n Mary" and that Verge was a nickname for Joseph. — Rachel
- I used to think virgin mary was actually 'virginia mary'Anon
- I thought the Holy Ghost was the ghost of the Virgin Mary.— Texas granny
- I thought the Virgin Islands were owned by Richard Branson until I was 24. — LJ
- I always thought 'virgin' was Marys star sign and could never work out why it was such a big dealAnon
- Instead of Madonnas 'Like a virgin' I used to sing 'Like a gerbil'— Stupid Child