1899, of notebooks, ledgers, etc. made to allow insertion or removal of pages at will, from loose (adj.) + leaf (n.) "page of a book."
Entries linking to loose-leaf
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.
leaf n.
Old English leaf "leaf of a plant, foliage; page of a book, sheet of paper," from Proto-Germanic *lauba- (source also of Old Saxon lof, Old Norse lauf, Old Frisian laf, Dutch loof, Old High German loub, German Laub "foliage, leaves," Gothic laufs "leaf, foliage"), perhaps from PIE *leub(h)- "to peel off, strip or break off" ((source also of Old Irish luib, "herb," lub-gort "garden;" Albanian labë "rind, cork;" Lithuanian luba "plank, board;" Russian lob "forehead, brow," Czech leb "skull;" Lithuanian luobas "bast," Latvian luobas "peel," Russian lub "bast;" Old Norse lyf "medicinal herbs," Old English lybb "poison; magic").
Related to lodge and lobby; for another PIE root see folio. Extended late 14c. to very thin sheets of metal (especially gold). Compare Lithuanian lapas "leaf," from a root also in Greek lepos "bark," lepein "to peel off." Also applied to flat and relatively broad surfaces, especially of flexible or mounted attachments; meaning "hinged flap on the side of a table" is from 1550s. To turn over a (new) leaf (1590s; 1570s as turn the leaf) "begin a new and better course of life" is a reference to the book sense. Among insects, leaf-hopper is from 1847; leaf-cutter from 1816.