reciprocation (n.) Look up reciprocation at Dictionary.com
1520s, "mode of expression;" 1560s, "act of reciprocating," from Latin reciprocationem (nominative reciprocatio) "retrogression, alternation, ebb," noun of action from past participle stem of reciprocare "move back, turn back," also "come and go, move back and forth;" from reciprocus (see reciprocal).