The expression "speak WASP?" comes from the TV show "Private Practice", where the main character, Addison would explain how her parents would never directly talk about important matters and would use a secret language instead.
*Sam and Addison are on the balcony watching Addison's parents talk about geraniums and drink martinis. Sam says it seems tense, but they look happy and are chatting about flowers*
Addison: "Trust me, they are not chatting about flowers. They are speaking WASP. We learn it at an early age."