تعریف و معنای "wet one's whistle"

What is the origin of the idiom "wet one's whistle" and when to use it?

The idiom "wet one's whistle" originates from the historical practice of using a whistle or flute-like instrument, often made of bone or wood, to summon a server or bartender at a tavern or inn. Over time, this act was associated with the need for a drink, leading to the idiom "wet one's whistle" as a way to request or consume a beverage.