laugh: [OE] The word laugh is ultimately onomatopoeic, imitative of the sound of laughter. It goes back to Indo-European *klak-, *klōk-, which also produced Greek klóssein, a verb denoting the clucking of hens, and Latin clangere ‘sound’ (source of English clangor [16]). Its Germanic descendants were *khlakh-, *khlōkh-, from which come German and Dutch lachen, Swedish and Danish le, and English laugh. => clangor
late 14c., from Old English (Anglian) hlæhhan, earlier hlihhan, from Proto-Germanic *klakhjan (cognates: Old Norse hlæja, Danish le, Old Frisian hlakkia, Old Saxon hlahhian, Middle Dutch and Dutch lachen, Old High German hlahhan, German lachen, Gothic hlahjan), from PIE *kleg-, of imitative origin (compare Latin cachinnare "to laugh aloud," Sanskrit kakhati "laughs," Old Church Slavonic chochotati "laugh," Lithuanian klageti "to cackle," Greek kakhazein). Originally with a "hard" -gh- sound, as in Scottish loch; the spelling remained after the pronunciation shifted to "-f."
If I coveted nowe to avenge the injuries that you have done me, I myght laughe in my slyve. [John Daus, "Sleidanes Commentaries," 1560]
1680s, from laugh (v.). Meaning "a cause of laughter" is from 1895; ironic use (as in that's a laugh) attested from 1930. Laugh track "canned laughter on a TV program" is from 1961.
