means The outer, colored peel of a citrus fruit, prized for its aromatic oils — or, by extension, lively enthusiasm and energy.

from From French 'zeste,' meaning the peel of an orange or lemon used as flavoring, which slipped into English in the 17th century. Its earlier roots are murky — possibly tracing to a word for the membrane dividing a walnut — but the citrus sense came first, and the figurative 'gusto, keen relish for life' followed naturally: the flavor you add to make things vivid.