Ha ha! I believe an eggcorn (it is an eggcorn, isn’t it Chris?) has been spotted in the wild on this very website (in the comments of the entry before this one)! Apparently, it’s a very common one: a search on google for "wet your appetite" gave 90,200 results, against 503,000 for the correct version, "whet your appetite". I ran to the library to find out that whet comes from Middle English whetten, from Old English hwettan, whereas wet comes from Old English wæt. The things I’d do to go out and enjoy this lovely autumn day.