Zest
Etymology
From French "zeste," originally the peel of an orange or lemon, of uncertain origin. Because citrus peel brightens and enlivens a dish, the word grew a figurative sense — “a zest for life” — of relish and vigor.
noun · /ZEST/
The fragrant, colored outer peel of a citrus fruit, grated for flavor — and, figuratively, keen enjoyment or energy.
What it names
The most aromatic part of a lemon or orange, and the same word doubles as a term for lively appetite for life.
Example
A little lemon zest lifts the whole cake with its bright, floral perfume.
Related idea
The prized counterpart of pith: zest is the thin, oil-rich colored layer full of flavor, while the pith just beneath it is the bitter white part you try to avoid.