For the longest time, I thought "granite" was the same word as "granted", so I thought that when somebody was "taking you for granted" it meant that you were going with them to collect rocks in the forest or something.
A childhood belief about speaking

others believed things like this
- I thought for the longest time that a No Standing traffic sign meant no person should stand near that sign.— Shannon
- For the longest time I thought 90210 was a sitcom Anon
- I used to believe that "nuptial" was a naughty word. I thought it meant nipple. XD— Sara Hagen
- i thought that you had like a box or something inside you to hold your soul for the longest time— jill
- I thought that Samson and Solomon from the Bible were the same person for the longest time...— Laura G.
- For years I heard the word "pedophile" and thought it meant a pedicurist's tool.— Lauren