Should
来自Big Physics
Old English sceolde : past of shall.
wiktionary
From Middle English scholde, from Old English scolde, first and third person preterite form of sculan(“should,” “have to,” “to owe”), the ancestor of English shall. Related to shild and shildy.
etymonline
should
c. 1200, from Old English sceolde, past tense of sceal (see shall). Preserves the original notion of "obligation" that has all but dropped from shall.
