Sumpter

Persuade me rather to be slave and sumpter / To this detested groom.

Source: wiktionary

the ancient vse of somers and sumpter horsses is in maner vtterlie relinquished

Source: wiktionary

The Bishop of Orange was watching carefully as men stored his papers in a cart, the King's steward and Despenser's bottler were stalking about among the wagons and sumpter horses ensuring that all was packed, while clerks of the various departments of state were hurrying about, squeaking at men who looked as though they might drop a chest or misstore a box in the wrong wagon, and generally getting in the way of everyone else while making themselves thoroughly miserable at the same time.

Source: wiktionary

You should have had a Sumpter , tho' 'thad cost me The laying on myself

Source: wiktionary