Etymology
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loose (adj.)

early 13c., lous, loos, lowse, "not securely fixed;" c. 1300, "unbound, not confined," from Old Norse lauss "loose, free, unencumbered; vacant; dissolute," cognate with Old English leas "devoid of, false, feigned, incorrect" (source of -less) from Proto-Germanic *lausaz (source also of Danish løs "loose, untied," Swedish lös "loose, movable, detached," Middle Dutch, German los "loose, free," Gothic laus "empty, vain"), from PIE root *leu- "to loosen, divide, cut apart."

Meaning "not clinging, slack" (of clothes, etc.) is from mid-15c. Meaning "not bundled" is from late 15c. Sense of "unchaste, immoral" ("lax in conduct, free from moral restraint") is recorded from late 15c. Meaning "at liberty, free from obligation" is 1550s. Sense of "rambling, disconnected" is from 1680s. As an adverb, "loosely," from 1590s. A loose end was an extremity of string, etc., left hanging; hence something unfinished, undecided, unguarded (1540s); to be at loose ends is from 1807. Phrase on the loose "free, unrestrained" is from 1749 (upon the loose). Colloquial hang loose is from 1968.

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loose (v.)
c. 1200, lousen, "to set free, turn loose," also "undo, untie, unfasten," from loose (adj.). Of arrows from c. 1400. Related: Loosed; loosing.
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loose-leaf (adj.)
1899, of notebooks, ledgers, etc. made to allow insertion or removal of pages at will, from loose (adj.) + leaf (n.) "page of a book."
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looseness (n.)
c. 1400, "freedom from restraint," from loose (adj.) + -ness. Meaning "laxity, irregularity, want of strictness" is from 1570s.
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footloose (adj.)
1690s, "free to move the feet, unshackled," from foot (n.) + loose (adj.). Figurative sense of "free to act as one pleases" is from 1873.
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loosely (adv.)
late 14c., from loose (adj.) + -ly (2). Similar formation in Dutch losselijk, Old Norse lausliga, Danish löselig.
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loose cannon (n.)

in the figurative sense "wildly irresponsible person, potent person or thing freed from usual restraint," by 1896; in the literal sense an object of dread on old warships; the figurative use probably arose from a celebrated scene in a popular late novel by Victor Hugo:

You can reason with a bull dog, astonish a bull, fascinate a boa, frighten a tiger, soften a lion; no resource with such a monster as a loose cannon. You cannot kill it, it is dead; and at the same time it lives. It lives with a sinister life which comes from the infinite. It is moved by the ship, which is moved by the sea, which is moved by the wind. This exterminator is a plaything. [Victor Hugo, "Ninety Three," 1874]
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fast and loose 
described as "a cheating game played with a stick and a belt or string, so arranged that a spectator would think he could make the latter fast by placing a stick through its intricate folds, whereas the operator could detach it at once." [James O. Halliwell, "Dictionary of Archaic and Provincial Words," 1847]. The figurative sense (1550s) is recorded earlier than the literal (1570s).
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unloose (v.)
mid-14c., "relax;" late 14c., "to set free," from un- (2), used here emphatically, + loose (v.). Old English had unliesan "unloose, set free." Related: Unloosed; unloosing.
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loosen (v.)
late 14c., losnen (transitive) "make loose, free from tightness," later lousen (early 15c.), from loose (v.) + -en (1). Intransitive sense of "become loose" is from 1670s. Meaning "limber the muscles before physical effort" is from 1955. Related: Loosened; loosening; loosener.
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