Sumpter
Sumpter , noun
[Old French sommetier the driver of a pack horse; akin to Old French & French sommier a pack horse, Latin sagmarius, from sagma a pack saddle, in Late Latin, a load, Greek {not transcribed} a pack saddle, from {not transcribed} to pack, load; compare Sanskrit saj, sañj, to hang on. Compare Seam a weight, Summer a beam.]
1.
The driver of a pack horse. [Obsolete] — Skeat
2.
A pack; a burden. [Obsolete] — Beau. & Fl
3.
An animal, especially a horse, that carries packs or burdens; a baggage horse. — Holinshed
Sumpter , adjective
Carrying pack or burdens on the back; as, a sumpter horse; a sumpter mule. — Bacon