Random Conversation: Selfish Drivers

Car passes us on the right in the shoulder:
Nat: Look at that car! Is that person being mean?
Dad: No. Selfish, perhaps, but not mean. Also dangerous.
Nat: [says like a tongue twister] Selfish shellfish. You know shellfish are not even fish! Selfish?
Dad: You know, selfish, like self, meaning you/yourself and -ish, meaning, like that. It means you only think of yourself.
Nat: Oh, that's what that means. I always wondered about that. I thought it was a kind of fish; a selfish. I thought it was a rude kind of fish and we just called people selfish because they would act like it.