indeed (adv.)youdaoicibaDictYouDict[indeed 词源字典]
early 14c., in dede "in fact, in truth," from Old English dæd (see deed). Written as two words till c. 1600. As an interjection, 1590s; as an expression of surprise or disgust, 1834. Emphatic form in yes (or no) indeedy attested from 1856, American English.[indeed etymology, indeed origin, 英语词源]