Word Origin & History
O.E. (Anglian) hlæhhan, earlier hlihhan, from P.Gmc. *klakhjanan (cf. O.N. hlæja, Ger. lachen, Goth. hlahjan), from PIE *klak-, of imitative origin (cf. L. cachinare "to laugh aloud," Skt. kakhati "laughs," O.C.S. chochotati "laugh," Gk. kakhazein).
"If I coveted nowe to avenge the injuries that you have done me, I myght laughe in my slyve." [John Daus, "Sleidanes Commentaries," 1560]
The noun is first attested 1680s, from the verb. Meaning "a cause of laughter" is from 1895; ironic use (e.g. that's a laugh) attested from 1930. Nitrous oxide has been called laughing gas since 1842 (for its exhilarating effects). Laugh track "canned laughter on a TV program" is from 1966.