Shag/shagged out

Popular British vulgarism for sexual intercourse and according to some sources dates from at least the 16th century. Its first appearance in print is in Classical Dictionary of the Vulgar Tongue compiled by Francis Grose in 1785. Its origin is unknown except that the word has archaic etymological connections to the word shake, which might be an allusion to the shaking that goes on before, during and after coitus. Shagged out is slang for exhausted, which derives from shag but first appears during the late 19th century.