1620s, "wrinkled" (of skin, etc.), past-participle adjective from corrugate (q.v.). The earlier adjective was simply corrugate (early 15c.), from Latin corrugatus. Meaning "bent into curves or folds" (of iron, cardboard, etc., for elasticity and strength) is from 1853.
1680s, "rubbing with a hard brush," verbal noun from scrub (v.). Scrubbing-brush is from 1680s. Scrubbing-board "washboard, corrugated board on which clothes are scrubbed" is by 1889.
"U-shaped iron bar with holes at the ends for a bolt or pin, used as a fastener," 1590s, of unknown origin; perhaps from a Scandinavian source akin to Old Norse klofi "a cleft," from Proto-Germanic *klub‑ "a splitting," from PIE root *gleubh- "to tear apart, cleave." Also uncertain is whether it is originally a plural or a singular.
1958, proprietary name (Britain), from French vel(ours) cro(ché) "hooked velvet."
Here is a nonmetallic fastener with no mechanical parts. It is simply two strips of nylon, one woven with thousands of tiny protruding hooks, the other with loops. Pressed together, they catch like a burr to clothing, can't be parted except by peeling. American Velcro, Manchester, N.H., makes them to hold anything from pants to upholstery. [Popular Science, December 1958]
"collarbone," 1610s, from French clavicule "collarbone" (16c.), also "small key," from Medieval Latin clavicula "collarbone" (used c. 980 in a translation of Avicenna), special use of classical Latin clavicula, literally "small key, bolt," diminutive of clavis "key" (from PIE root *klau- "hook"); in the anatomical sense a loan-translation of Greek kleis "key, collarbone," which is from the same PIE source. So called supposedly from its function as the "fastener" of the shoulder. Related: Clavicular.