Fossil word
A fossil word is a word that is broadly obsolete but remains in use due to its presence in an idiom or phrase. An example of a word is 'ado' in 'much ado'. An example of a phrase is 'in point', which is found in the phrases 'case in point' and 'in point of fact', but is rarely used outside of a legal context.
ado, as in "without further ado" or "with no further ado" or "much ado about nothing", although the homologous form "to-do" remains attested amok, as in "run amok"asunder, as in "torn asunder"bandy, as in "bandy about" or "bandy-legged"bated, as in "wait with bated breath", although the derived term "abate" remains in non-idiom-specific usebeck, as in "at one's beck and call", although the verb form "beckon" is still used in non-idiom-specific usebetide, as in "woe betide you/us/them"bide, as in "bide your time"champing, as in "champing at the bit", where "champ" is an obsolete precursor to "chomp", in current usecoign, as in "coign of vantage"deserts, as in "just deserts", although singular "desert" in the sense of "state of deserving" occurs in nonidiom-specific contexts including law and philosophy. "Dessert" is a French loanword, meaning "removing what has been served," and has only a distant etymological connection.dint, as in "by dint of"dudgeon, as in "in high dudgeon"eke, as in "eke out"fettle, as in "in fine fettle", although the verb, 'to fettle', remains in specialized use in metal casting.fro, as in "to and fro"goodly, as in "goodly number"helter skelter, as in "scattered helter-skelter about the office", Middle English skelten to hasteninclement, as in "inclement weather”jetsam, as in "flotsam and jetsam", except in legal contexts kith, as in "kith and kin"lam, as in “on the lam”lo, as in "lo and behold"loggerheads as in "at loggerheads" or loggerhead turtlemadding as in "far from the madding crowd"math, as in "aftermath"muchness as in "much of a muchness"ne'er, as in "ne'er-do-well"scot, as in "scot free"sleight, as in "sleight of hand"shebang, as in "the whole shebang", although the word is now used as an unrelated common noun in programmers' jargon.shrive, preserved only in inflected forms occurring only as part of fixed phrases: 'shrift' in "short shrift" and 'shrove' in "Shrove Tuesday"span and spick, as in "spick and span"turpitude, as in "moral turpitude"vim, as in "vim and vigor", though preserved as the name of a scouring powderwedlock, as in "out of wedlock"wend, as in "wend your way", although its former past tense "went" is still in use as the past tense of "to go"wreak, as in "wreak havoc"yore, as in "of yore", usually "days of yore"
"Born fossils"
These words were formed from other languages, by elision, or by mincing of other fixed phrases.caboodle, as in "kit and caboodle" druthers, as in "if I had my druthers..." tarnation, as in "what in tarnation...?" nother, as in "a whole nother..."