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.

Definitions of answer
answer (v.)
react verbally;
We answered that we would accept the invitation
answer the question
She didn't want to answer
Synonyms: reply / respond
answer (v.)
respond to a signal;
answer the telephone
answer the door
answer (v.)
give the correct answer or solution to;
answer a question
answer the riddle
answer (v.)
understand the meaning of;
The question concerning the meaning of life cannot be answered
Synonyms: resolve
answer (v.)
give a defence or refutation of (a charge) or in (an argument);
The defendant answered to all the charges of the prosecution
answer (v.)
be liable or accountable;
She must answer for her actions
answer (v.)
be sufficient; be adequate, either in quality or quantity;
A few words would answer
Synonyms: suffice / do / serve
answer (v.)
match or correspond;
The drawing of the suspect answers to the description the victim gave
answer (v.)
be satisfactory for; meet the requirements of or serve the purpose of;
This may answer her needs
answer (v.)
react to a stimulus or command;
The steering of my new car answers to the slightest touch
answer (n.)
a statement (either spoken or written) that is made to reply to a question or request or criticism or accusation;
I waited several days for his answer
Synonyms: reply / response
answer (n.)
a statement that solves a problem or explains how to solve the problem;
the answers were in the back of the book
answer (n.)
the speech act of replying to a question;
answer (n.)
the principal pleading by the defendant in response to plaintiff's complaint; in criminal law it consists of the defendant's plea of `guilty' or `not guilty' (or nolo contendere); in civil law it must contain denials of all allegations in the plaintiff's complaint that the defendant hopes to controvert and it can contain affirmative defenses or counterclaims;
answer (n.)
a nonverbal reaction;
his answer to any problem was to get drunk
their answer was to sue me