whet somebody's appetite
whet (one's) appetite
To induce or increase one's interest in something. The first chapter of that novel really whetted my appetite—I'm eager to read more of it tonight.
ˌwhet somebody’s ˈappetitemake somebody feel hungry; make somebody interested in something: Don’t eat too much of this dish. It’s only to whet your appetite for the main course. ♢ One of my teachers lent me a book about climbing, and it really whetted my appetite.
If you whet a knife, sword, etc., you make it sharper.