means A pungent yellow or brown condiment made from ground mustard seeds, used to spice up sandwiches, sausages, and dressings.

from From Old French 'moustarde,' which comes from 'moust' (must — the freshly pressed, unfermented grape juice) plus a suffix, because the ground seeds were originally mixed into that sweet must to make the paste. The Old French 'moust' traces back to Latin 'mustum.' So the name remembers a recipe: seeds meet new wine. The seed-bearing plant lent its name to the sauce, not the other way around — and only later did 'mustard' come to mean the color of the finished spread.