I've never read Catcher in the Rye but it came up in conversation when discussing how reading new words can be hard, especially atypical names. Apparently, J.D. Salinger used the wrong word (repeatedly)
https://www.grammarly.com/blog/crummy-crumby/
Crummy and crumby are both valid words, but they mean different things. Crumby means “full of crumbs.” Crummy means “lousy.” In British English, crumby and…