wet one's whistle

Idioms  

1. Have a drink, as in I'm just going to wet my whistle before I go out on the tennis court. This expression uses whistle in the sense of “mouth” and may allude to the fact that it is very hard to whistle with dry lips. [Late 1300s]

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Example Sentences

A superstitious practice among old seamen, who are equally scrupulous to avoid whistling during a heavy gale.—To wet one's whistle.

From The Sailor's Word-Book An Alphabetical Digest of Nautical Terms, including Some More Especially Military and Scientific, but Useful to Seamen; as well as Archaisms of Early Voyagers, etc. by Belcher, Edward, Sir