Is it ensure, insure, or assure?
"defeated," c.1300; "wasted, spent in vain," c.1500; also "no longer to be found" (1520s), from past participle of lose. Lost Cause in reference to the Southern U.S. bid for independence is from the title of E.A. Pollard's history of the CSA and the rebellion (1866). Lost Generation in reference to the period 1914-18 first attested 1926 in Hemingway's "The Sun Also Rises," where he credits it to Gertrude Stein.
An exclamation of severe and abrupt rejection; drop deadverb phrase
To leave; depart; scram • Usually an exasperated command: If the cops or I ask her a direct question, she'll tell us to get lost (1940s+)