Answer
Old English andswaru (noun), andswarian (verb), of Germanic origin; from a base shared by swear.
wiktionary
From Middle English answere, andsware, from Old English andswaru(“answer”), from and-(“against”) + -swaru(“affirmation”), (from Proto-Indo-European *h₂ent-(“front, forehead”) and Old English swerian(“to swear”), from Proto-Indo-European *swer-), suggesting an original meaning of "a sworn statement rebutting a charge". The cognates suggest the existence of Proto-Germanic *andaswarō(“a reply to a question”). Cognate with Old Frisian ondser(“answer”), Old Saxon andswōr(“answer”), Danish and Swedish ansvar(“liability, responsibility, answer”), Icelandic andsvar(“answer, response”). Compare also Old English andwyrde(“answer”) (cognate to Dutch antwoord, German Antwort), Old English andcwiss(“reply”), German Schwur(“oath, vow”).
From Middle English answeren, andswaren, answerien, from Old English andswarian, answarien(“to answer, to respond, to deny an allegation under oath”), from Proto-Germanic *andaswarōną, *andaswarjaną(“to answer, to give a response, to rebut”), from *anda-(“against”) + *swarjaną, *swarōną(“to swear an oath, to answer, to respond”), from Proto-Indo-European *swer-(“to swear”) and *h₂ent-(“face, forehead”), equivalent to and-(“against, back”) + swear. Cognate with Old Frisian ondswera(“to answer”), Danish ansvare(“to answer, account for”), Swedish ansvara(“to answer, account for”), Icelandic andsvara(“to answer, reply”).
etymonline
answer (n.)
Old English andswaru "a response, a reply to a question," from and- "against" (from PIE root *ant- "front, forehead," with derivatives meaning "in front of, before") + -swaru "affirmation," from swerian "to swear" (see swear), suggesting an original sense of "sworn statement rebutting a charge." Meaning "solution of a problem" is from c. 1300.
It is remarkable that the Latin expression for answer is formed in exactly the same way from a verb spondere, signifying to engage for, to assure. [Hensleigh Wedgwood, "A Dictionary of English Etymology," 1859]
A common Germanic compound (cognates: Old Saxon antswor, Old Norse andsvar, Old Frisian ondser, Danish and Swedish ansvar), implying a Proto-Germanic *andswara-. The simpler idea of "a word in reply" is expressed in Gothic anda-vaurd, German Antwort.
answer (v.)
Old English answarian "make a statement in reply," from and- "against" (from PIE root *ant- "front, forehead," with derivatives meaning "in front of, before") + swerian "to swear" (see swear), suggesting an original sense of "make a sworn statement rebutting a charge."
Meanings "conform, correspond" and "be responsible for" are from early 13c; that of "suffer the consequences of" is from late 13c.; that of "respond in antiphony" is from early 15c. Sense of "respond in act or action, give back in kind" is from 1570s; that of "solve, find the result of" is from 1742. Related: Answered; answering. The telephone answering machine so called from 1961.
