adamant (n.)youdaoicibaDictYouDict[adamant 词源字典]
mid-14c., from Old French adamant and directly from Latin adamantem (nominative adamas) "adamant, hardest iron, steel," also figuratively, of character, from Greek adamas (genitive adamantos) "unbreakable, inflexible" metaphoric of anything unalterable, also the name of a hypothetical hardest material, perhaps literally "invincible," from a- "not" + daman "to conquer, to tame" (see tame (adj.)), or else a word of foreign origin altered to conform to Greek.

Applied in antiquity to a metal resembling gold (Plato), white sapphire, magnet (by Ovid, perhaps via confusion with Latin adamare "to love passionately"), steel, emery stone, and especially diamond (see diamond). "The name has thus always been of indefinite and fluctuating sense" [Century Dictionary]. The word was in Old English as aðamans "a very hard stone."[adamant etymology, adamant origin, 英语词源]
diamond (n.)youdaoicibaDictYouDict
early 14c., from Old French diamant, from Medieval Latin diamantem (nominative diamas), from Vulgar Latin *adiamantem (altered by influence of the many Greek words in dia-), from Latin adamantem (nominative adamans) "the hardest metal," later, "diamond" (see adamant). Playing card suit is from 1590s; Sense in baseball is American English, 1875.
enamel (n.)youdaoicibaDictYouDict
early 15c., in ceramics, from enamel (v.). As "hardest part of a tooth," 1718, from a use in French émail.
KedyoudaoicibaDictYouDict
proprietary name of a brand of canvas sneakers, 1917, registered by United States Rubber Co., N.Y. Based on Latin ped-, stem of pes "foot" (see foot (n.))
"We wanted to call it Peds, but ... it came too close to ... other brand names. So we batted it around for awhile and decided on the hardest-sounding letter in the alphabet, K, and called it Keds, that was in 1916." [J.Healey, in R.L. Cohen, "Footwear Industry," x.93]
logrolling (n.)youdaoicibaDictYouDict
also log-rolling, in the legislative vote-trading sense, 1823, American English, from the notion of neighbors on the frontier helping one another with the heavy work of clearing land and building cabins (as in phrase you roll my log and I'll roll yours); see log (n.1) + rolling.
LOG-ROLLING. 1. In the lumber regions of Maine it is customary for men of different logging camps to appoint days for helping each other in rolling the logs to the river, after they are felled and trimmed -- this rolling being about the hardest work incident to the business. Thus the men of three or four camps will unite, say on Monday, to roll for camp No. 1, -- on Tuesday for camp No. 2, -- on Wednesday for camp No. 3, -- and so on, through the whole number of camps within convenient distance of each other. [Bartlett]