Etymology
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sharpen (v.)

late 14c., sharpenen, "intensify;" mid-15c., "make a point sharp or sharper," from sharp (adj.) + -en (1). Related: Sharpened; sharpening. The older verb was simply sharp (Middle English sharpen), from the adjective and partly from Old English gescirpan (West Saxon), scerpan (Anglian) "to score, scarify;" also compare scearpung "scarifying."

To sharpen (one's) pencil in the figurative sense of "prepare to get to work" is by 1957, American English.

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acrid (adj.)

1712, "sharp and bitter to the taste," formed irregularly (perhaps by influence of acrimonious) from Latin acer (fem. acris) "sharp to the senses, pungent, bitter; eager, fierce," also figuratively, of qualities, "active, ardent, spirited," also "hasty, quick, passionate;" of mind "violent, vehement; subtle, penetrating," from PIE *akri- "sharp," from root *ak- "be sharp, rise (out) to a point, pierce." Of feelings, temper, etc., in English from 1781. The -id suffix probably is in imitation of acid. Acrious (1670s) is a correct formation, but seldom seen. Related: Acridly.

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beetle (v.)
"project, overhang," apparently a Shakespearean back-formation (in "Hamlet," 1602) from bitelbrouwed "grim-browed, sullen" (mid-14c.), from bitel "sharp-edged, sharp" (c. 1200), probably a compound from Old English *bitol "biting, sharp" (related to bite (v.)), + brow, which in Middle English meant "eyebrow," not "forehead." Meaning "to overhang dangerously" (of cliffs, etc.) is from c. 1600. Related: Beetled; beetling.
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clack (n.)

"a sharp, repeated, rattling sound," mid-15c., from clack (v.).

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clang (n.)

"a loud, sharp, resonant, metallic sound," 1590s, from clang (v.).

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amblyopia (n.)

1706, "weakening of the eyesight without any apparent defect in the eyes," medical Latin, from Greek amblyōpia "dim-sightedness," noun of action from ōps "eye" (from PIE root *okw- "to see")  + amblys "dulled, blunt," a word of uncertain origin; according to Watkins possibly from a suffixed form of PIE root *mel- (1) "soft." With abstract noun ending -ia. Related: Amblyopic.

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acute (adj.)

late 14c., originally of fevers and diseases, "coming quickly to a crisis" (opposed to chronic), from Latin acutus "sharp, pointed," figuratively "shrill, penetrating; intelligent, cunning," past participle of acuere "to sharpen" (literal and figurative), from PIE root *ak- "be sharp, rise (out) to a point, pierce."

It was also used of humors (early 15c.). The meaning "ending in a sharp point" is from 1560s; the sense of "sharp or penetrating in intellect" is from 1580s. Of feelings, pains, etc., "intense," 1727. As a noun, early 15c. of fevers; c. 1600 as "an acute accent." Related: Acutely; acuteness.

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acervate (v.)

"to heap up," 1610s, from Latin acervatus, past participle of acervare "to heap up," from acervus "heap," which is akin to acer "sharp" (from PIE root *ak- "be sharp, rise (out) to a point"). Related: Acervated; acervating; acerval; acervative; acervuline "occurring in clusters; clustered" (by 1859).

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tip (n.2)
"a light, sharp blow or tap," mid-15c., from tip (v.3).
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snag (n.)
1570s, "stump of a tree, branch," of Scandinavian origin, compare Old Norse snagi "clothes peg," snaga "a kind of ax," snag-hyrndr "snag-cornered, with sharp points." The ground sense seems to be "a sharp protuberance." The meaning "sharp or jagged projection" is first recorded 1580s; especially "tree or branch in water and partly near the surface, so as to be dangerous to navigation" (1807). The figurative meaning "obstacle, impediment" is from 1829.
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