The French condiment name derives from a word for must, tracing to Latin mustum.
Middle English is compressed in the card sequence. The must card is a noun, not the obligation verb.
Sources
- Merriam-Webster: mustard
The entry gives the Latin and two French formation steps.
- Merriam-Webster: must
The grape-juice noun traces to Latin and is separate from the obligation verb.
- Anglo-Norman Dictionary · mustarde
Meanings of the older forms on the word path.
- Online Etymology Dictionary · mustard
Meanings of the older forms on the word path.
- Anglo-Norman Dictionary · must 1
Meanings of the older forms on the word path.