It’s probably not that unusual for kids who hang out with the super-sarcastic crowd in grade school. If you ever came home crying about being called a shallow, pedestrian puddle gargler, I have no memory of it, however.
It could be that pedestrian crossed in your mind with something genuinely nasty like pederast, in which case, I’m sorry I brought that up.
There are a lot a vaguely insulting words that start with ped-, it seems to me: pedagogue, pedant, pedunculate barnacle… Maybe that’s because ped- is “foot” and “child” and “earth”, so dealing with lowly stuff or at least things that are close to the ground.
In any case, your memory probably has a few other meandering terms that landed in the minor mistake pile, so remember: if you use the wrong word, just be sure to do it REAL LOUD!!