seasoning n.

late 14c., sesounen, "improve the flavor of by adding spices," from season (n.) and from Old French saisonner "to ripen, season" (Modern French assaisoner), from seison, saison "right moment, appropriate time" on the notion of fruit becoming more palatable as it ripens.

Figurative use by 1510s. Of timber, etc., "bring to maturity by prolonged exposure to some condition," by 1540s; hence in extended sense "bring to the best condition or use; of persons "fit to any use by time or habit," c. 1600. In 16c., it also meant "to copulate with." Intransitive sense of "become mature, grow fit for use" is by 1670s.