出典:Wiktionary
amids + -t (excrescent), from amid + -s (genitive); surface analysis as amid + -st (excrescent). Root amid from Middle English amidde, amiddes, on midden, from 古期英語 on middan (“in the middle”), from midd (“central”) (English mid).
amidst
As with other words with excrescent suffix -st, amidst is generally considered synonymous with simpler amid, and amid is preferred by style guides on both sides of the Atlantic.[1]
Further, amidst/amid are similar in meaning to – but distinct from – amongst/among. Amid(st) denotes that something is "in the midst of", "surrounded by" other things, and is used when the idea of separate things is not prominent. Among(st) denotes that something is mingling with other separable things ("blessed art thou among women").
Some speakers feel it is an obsolete form of amid. Amidst is more common in British English than American English, though it is used to some degree in both.