Etymology
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live (adj.)

1540s, "having life, not dead," a shortening of alive (q.v.). From 1610s of fire, coal, etc., "burning, glowing;" 1640s of things, conditions, etc., "full of active power;" sense of "containing unspent energy or power" (live ammunition) is from 1799.

Meaning "in-person, not recorded" (of performance) is attested by 1917. Live wire is attested from 1890, "circuit through which an electric current is flowing;" figurative sense of "active person" is from 1903. Jocular real live "genuine" is from 1887. The older adjective is lively.

A GRIM RECORD — The death harvest of the "live wire" and "third rail" goes right on. It is not governed by seasons nor, qualified by time. It is the ubiquitous epidemic of electricity, defiant of doctors and ruthless as fate. [The Insurance Press, Aug. 22, 1900]
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live (v.)

Middle English liven, from Old English lifian (Anglian), libban (West Saxon) "to be, be alive, have life; continue in life; to experience," also "to supply oneself with food, procure a means of subsistence; pass life in a specified fashion," from Proto-Germanic *libejanan (source also of Old Norse lifa "to be left; to live; to live on," of fire, "to burn;" Old Frisian libba, German leben, Gothic liban "to live"), from PIE root *leip- "to stick, adhere," forming words meaning "to remain, continue."

Meaning "to make a residence, dwell" is from c. 1200. Meaning "express in one's life" (live a lie) is from 1540s. Intensified sense "have life abundantly, make full use of life's opportunities" is from c. 1600. Related: Lived; living.

To live it up "live gaily and extravagantly" is from 1903. To live up to "act in accordance with, not live below the standard of" is 1690s, from earlier live up "live on a high (moral or mental) level" (1680s). To live (something) down "cause (something disreputable) to be forgotten by subsequent blameless course, live so as to disprove" is from 1842. To live with "cohabit as husband and wife" is attested from 1749; sense of "to put up with" is attested from 1937. Expression live and learn is attested from c. 1620.

According to the Dutch Prouerbe ... Leuen ende laetan leuen, To liue and to let others liue. [Gerard de Malynes, 1622]
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on- 

the preposition and adverb on used as a prefix; Old English on-, an-.

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-on 
subatomic particle suffix, from ion.
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on (prep., adv.)

"in a position above and in contact with; in such a position as to be supported by;" also noting the goal to which some action is or has been directed; "about, concerning, regarding; in a position to cover;" as an adverb, "in or into a position in contact with and supported by the top or upper part of something; in or into place; in place for use or action; into movement or action; in operation," Old English on, unstressed variant of an "in, on, into," from Proto-Germanic *ana "on" (source also of Dutch aan, German an, Gothic ana "on, upon"), from PIE root *an- (1) "on" (source also of Avestan ana "on," Greek ana "on, upon," Latin an-, Old Church Slavonic na, Lithuanian nuo "down from").

Also used in Old English in many places where we now would use in. From 16c.-18c. (and still in northern England dialect) often reduced to o'. Phrase on to "aware" is from 1877.

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clip-on (adj.)

"held on by means of a clip," 1909, from the verbal phrase; see clip (v.2) + on (adv.).

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hang on (v.)
1860, "to remain clinging," 1860, especially "cling fondly to" (1871); see hang (v.) + on (adv.). As a command to be patient, wait a minute, from 1936, originally in telephone conversations.
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live-in (adj.)
"residing on the premises," 1950, from live (v.) + in (adv.). To live out was formerly "be away from home in domestic service."
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live-oak (n.)
evergreen oak tree of the U.S. South, c. 1600, from live (adj.) + oak (n.).
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hard-on (n.)
"penile erection," 1922, earlier as an adjective (1893), from hard + on.
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