A childhood belief about general

For a long time (from when I was about 3 to when I was 7) I thought that whenever my sister or brother grew a lot, and my parents mentioned it, that they had a 'gross purt', or a grosspurt. I really never could find out why anyone wanted to have a gross purt, but my siblings seemed to think that it was cool whenever they had a grosspurt, so eventually I accepted that they were okay. (I also never knew what a growth spurt was when I read it in a book...I started reading really early)
I didn't differentiate the two terms for a long time. Finally, one day, I realized that it really was a growth spurt. It's a lot less interesting, but it make a whole lot more sense.