英语词源字典 - 在线词源网站

assured (adj.)[assured 词源字典]: of persons, "confident, self-assured," late 14c., past participle adjective from assure. Related: Assuredly; assuredness. [assured etymology, assured origin, 英语词源]
certain (adj.): c. 1300, "determined, fixed," from Old French certain "reliable, sure, assured" (12c.), from Vulgar Latin *certanus, from Latin certus "sure, fixed, settled, determined" (also source of Italian certo, Spanish cierto), originally a variant past participle of cernere "to distinguish, decide," literally "to sift, separate" (see crisis).

Of persons, "full of confidence in one's knowledge or judgment," from mid-14c. Euphemistic use (of a certain age, etc.) attested from mid-18c. Certainer, certainest were common to c. 1750, but have fallen from proper use for some reason. Expression for certain "assuredly" is attested by early 14c.
hardly (adv.): c. 1200, "in a hard manner, with great exertion or effort," from Old English heardlice "sternly, severely, harshly; bravely; excessively" (see hard (adj.) + -ly (2)). Hence "assuredly, certainly" (early 14c.). Main modern sense of "barely, just" (1540s) reverses this, via the intermediate meaning "not easily, with trouble" (early 15c.). Formerly with superficial negative (not hardly). Similar formation in Old Saxon hardliko, German härtlich, Old Danish haardelig.
Hercules: hero, son of Zeus and Alcmene, c. 1200 (originally in reference to the Pillars of Hercules), also Ercules, from Latin Hercles, from Greek Herakles, literally "Glory of Hera;" from Hera (q.v.) + kleos "glory, renown" (see Clio). Used figuratively of strength since late 14c. Vocative form Hercule was a common Roman interjection (especially me Hercule!) "assuredly, certainly."
redhead (n.): mid-13c., from red (adj.1) + head (n.). Red (adj.), of persons, "having red hair" is from late Old English.
The Carrot pate be sure you hate, for she'l be true to no man,
But put her too 't and she will do 't, and oft turns very common:
She that is red upon the head will doubtless ne'r forsake it,
But wanton be, assuredly, and willingly will take it.
["The True Lover's Admonition," Roxburghe Ballads, c. 1680]
sure (adj.): early 13c., "safe against attack, secure," later "firm, reliable" (c. 1300); "mentally certain, confident" (mid-14c.); "firm, strong, resolute" (c. 1400), from Old French seur, sur "safe, secure; undoubted, dependable, trustworthy" (12c.), from Latin securus "free from care, untroubled, heedless, safe" (see secure (adj.)). Pronunciation development is that of sugar (n.).

As an affirmative meaning "yes, certainly" it dates from 1803, from Middle English meanings "firmly established; having no doubt," and phrases like to be sure (1650s), sure enough (1540s), and for sure (1580s). The use as an adverb meaning "assuredly" goes back to early 14c. Sure-footed is from 1630s, literal and figurative; sure thing dates from 1836. In 16c.-17c., Suresby was an appellation for a person to be depended upon.