1570s, "spiny, full of sharp points, armed with prickles" (originally of holly leaves), from prickle (n.) + -y (2). Figurative sense of "irritable, quick to anger" is recorded by 1862. Prickly heat "inflammatory disorder of the sweat glands" is from 1736, so called for the sensation; prickly pear, of the fruit of a certain cactus, is from 1760 (earlier prickle pear, 1610s). Related: Prickliness.
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.
"to turn over (the pages of a book)," 1660s, from leaf (n.). Meaning "put forth leaves or foliage" is from 1610s. Related: Leafed; leaved; leafing.
1590s, "having a sharp edge;" 1690s, "having a hem or border," past-participle adjective from edge (v.).
ancient type of Celtic dagger found in Ireland, double-edged and leaf-like, 1520s, from Irish Gaelic scian (genitive sceine) "knife," cognate with Gaelic sgian "knife," Welsh ysgien "a slicer," from PIE *skiy-ena-, from root *skei- "to cut, split."