Etymology
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blade (n.)
Old English blæd "a leaf," also "a leaf-like part" (of a spade, oar, etc.), from Proto-Germanic *bladaz (source also of Old Frisian bled "leaf," German Blatt, Old Saxon, Danish, Dutch blad, Old Norse blað), from PIE *bhle-to-, suffixed form (past participle) of root *bhel- (3) "to thrive, bloom."

Extended in Middle English to the broad, flattened bone of the shoulder (c. 1300) and the cutting part of knives and swords (early 14c.). The modern use in reference to grass may be a Middle English revival, by influence of Old French bled "corn, wheat" (11c.), which is perhaps from Germanic. The cognate in German, Blatt, is the general word for "leaf;" Laub is used collectively as "foliage." Old Norse blað was used of herbs and plants, lauf in reference to trees. This might have been the original distinction in Old English, too. Compare leaf (n.). Of men from 1590s; in later use often a reference to 18c. gallants and dashing rakes, but the original exact sense, and thus signification, is uncertain.
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rotor (n.)

1873, an irregular shortening of rotator, originally in mathematics. Mechanical sense of "rotating part of a motor" is attested by 1903; specifically of helicopters from 1930.

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Rototiller (n.)

machine with rotating blades to break up soil, 1923, from roto-, perhaps based on the mechanical use of rotor, + tiller

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stator (n.)

"stationary part of a generator" (opposed to rotor), 1895, from Latin stator, agent noun from stare "to stand" (from PIE root *sta- "to stand, make or be firm"). In classical Latin it meant "an orderly, attendant upon a proconsul."

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switchblade (n.)
also switch-blade, type of folding pocket knife, 1932, from switch (n.) + blade. So called for the "switch" which is pressed to spring the knife open. Earlier a similar tool was known as an Arkansas toothpick (1837) and a clasp-knife (1755).
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coulter (n.)

also colter, "iron blade or sharp-edged wheel attached to the beam of a plow to cut the ground," Old English culter, from Latin culter "a knife, iron blade in a plowshare," from PIE root *skel- (1) "to cut." As a surname (13c.), probably from Coulter in Lancashire.

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rotator (n.)

1670s, "muscle which allows a part to be moved circularly," agent noun from Latin rotare "turn round, revolve" (see rotary). Also compare rotor. General mechanical sense of "one who or that which rotates" is by 1772. Related: Rotatory.

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peel (n.2)

"wooden shovel with a broad blade and a long handle," used by bakers, etc., late 14c.. pele, from Old French pele (Modern French pelle) "shovel," from Latin pala "spade, shovel, baker's peel, shoulder blade," related to pangere "to insert firmly," probably from PIE *pag-slo-, suffixed form of root *pag- "to fasten."

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broadsword (n.)
"sword with a broad blade," Old English brad swurd, from broad (adj.) + sword.
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palette (n.)

1620s, "flat, thin tablet, with a hole at one end for the thumb, used by an artist to lay and mix colors," from French palette, from Old French palete "small shovel, blade" (13c.) diminutive of pale "shovel, blade," from Latin pala "spade, shoulder blade," probably from PIE *pag-slo-, suffixed form of root *pag- "to fasten." Transferred sense of "colors used by a particular artist" is from 1882. Palette-knife, originally one used by artists for mixing colors, is attested by 1759.

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