Etymology
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sing (v.)

Old English singan "to chant, sing, celebrate, or tell in song," also used of birds (class III strong verb; past tense sang, past participle sungen), from Proto-Germanic *sengwan (source also of Old Saxon singan, Old Frisian sionga, Middle Dutch singhen, Dutch zingen, Old High German singan, German singen, Gothic siggwan, Old Norse syngva, Swedish sjunga), from PIE root *sengwh-"to sing, make an incantation."

There are said to be no related forms in other languages, unless perhaps it is connected to Greek omphe "voice" (especially of a god), "oracle;" and Welsh dehongli "explain, interpret." The typical Indo-European root is represented by Latin canere (see chant (v.)). Other words meaning "sing" derive from roots meaning "cry, shout," but Irish gaibim is literally "take, seize," with sense evolution via "take up" a song or melody.

The criminal slang sense of "to confess to authorities" is attested from 1610s. 

Every child should be taught, from its youth, to govern its voice discreetly and dexterously, as it does its hands ; and not to be able to sing should be more disgraceful than not being able to read or write. For it is quite possible to lead a virtuous and happy life without books, or ink ; but not without wishing to sing, when we are happy ; nor without meeting with continual occasions when our song, if right, would be a kind service to others. [Ruskin, "Rock Honeycomb"]
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