reciprocate

The story

1. Latin · borrowed fromrecīprocātus
2. English todayreciprocate

From Latin recīprocātus, perfect passive participle of recīprocō (“to move back and forth”) (see -ate (verb-forming suffix)), from reciprocus (“back an forth, reciprocal, alternating”) + -ō (first conjugation verb-forming suffix), itself possibly from a phrase such as reque proque (“back and forth”), from re- (“back”), prō (“forwards”) and -que (“and”). See also reciprocal. Compare French réciproquer.