1670s, from French zeste "piece of orange or lemon peel used as a flavoring," of unknown origin. Sense of "thing that adds flavor" is 1709; that of "keen enjoyment" first attested 1791.
Entries linking to zest
zestful adj.
1797, from zest + -ful. Related: Zestfully; zestfulness.
zesty adj.
1789, from zest + -y (2). Related: Zestily; zestiness.