"person of moderate or intermediate political views," 1872, from French centriste, from centre (see center (n.)). Originally in English with reference to French politics; general application to other political situations is by 1889.
Where M. St. Hilaire is seen to most advantage, however, is when quietly nursing one of that weak-kneed congregation who sit in the middle of the House, and call themselves "Centrists." A French Centrist is—exceptis eoccipiendis—a man who has never been able to make up his mind, nor is likely to. ["Men of the Third Republic," London, 1873]
1846, "capable of being declared as true," from certify + -able. The meaning "so deranged as to be certifiably insane" is recorded from 1870, from certify in the specific sense "officially declare (someone) to be insane" (1822). The certification was done by local officials, later medical officers, and often included a statement as to whether the person was harmless or dangerous, curable or incurable.
early 15c., "ligament in the neck," from Latin cervix "the neck, nape of the neck," from PIE *kerw-o-, from root *ker- (1) "horn; head." Applied to various neck-like structures of the body, especially that of the uterus (by 1702), where it is shortened from medical Latin cervix uteri (17c.). Sometimes in 18c.-19c. medical writing it is cervix of the uterus to distinguish it from the neck.
late 14c., "a relinquishing, act of yielding," from Old French cession "cession; death" (13c.), from Latin cessionem (nominative cessio) "a giving up, surrendering," noun of action from past-participle stem of cedere "to go away, yield" (from PIE root *ked- "to go, yield"). Related: Cessionary.
"consisting of 100 degrees, divided into 100 equal parts," 1799, from French, from centi- "hundred" (see centi-) + second element from Latin gradi "to walk, go, step" (from PIE root *ghredh- "to walk, go"). The centigrade thermometer (see Celsius) divides the interval between the freezing and boiling points of water into 100 degrees.
"certainty, complete assurance," early 15c., from Old French certitude "certainty" and directly from Late Latin certitudinem (nominative certitudo) "that which is certain," from Latin certus "sure, certain" (see certain).
mid-15c., cessacyoun "interruption, a ceasing; abdication," from Latin cessationem (nominative cessatio) "a delaying, ceasing, tarrying," noun of action from past-participle stem of cessare "to delay" (from PIE root *ked- "to go, yield").
also cess-pool, "cistern or well to receive sediment or filth," 1670s, the first element perhaps an alteration of cistern, or perhaps a shortened form of recess [Klein]; or the whole may be an alteration of suspiral (c. 1400), "drainpipe," from Old French sospiral "a vent, air hole," from sospirer "breathe," from Latin suspirare "breathe deep" [Barnhart]. Meaning extended to "tank at the end of the pipe," which would account for a possible folk-etymology change in final syllable.
Other possible etymologies: Italian cesso "privy" [OED], from Latin secessus "place of retirement" (in Late Latin "privy, drain"); dialectal suspool, from suss, soss "puddle;" or cess "a bog on the banks of a tidal river."