atone (v.) Look up atone at Dictionary.com
1550s, from adverbial phrase atonen (c.1300) "in accord," literally "at one," a contraction of at and one. It retains the older pronunciation of one. The phrase perhaps is modeled on Latin adunare "unite," from ad- "to, at" (see ad-) + unum "one." Related: Atoned; atoning.