vanilla

Where it comes from

Vanilla comes from Spanish vainilla, little sheath or little pod, the diminutive of vaina, sheath. Spanish vaina descends from Latin vagina, a sheath or scabbard; the plant was named for the shape of its long fruit.

How the meaning developed

The pod's name passed to the flavor extracted from it. Because vanilla became a familiar default flavor, especially in ice cream and mass-market products, English later made vanilla an adjective for plain, conventional, or unmodified.