seton
A few silk threads or horsehairs, or a strip of linen etc., introduced beneath the skin by a knife or needle, so as to induce suppuration; also, the issue so formed.
If the predisposition to the disease has arisen from a plethoric state of the system, or from a turgescence in the vessels of the head, this is to be obviated by bleeding, both generally and topically, but more particularly the latter; an abstemious diet and proper exercise; and by a seton in the neck.
Where it comes from
From Middle English seton, setoun, from Medieval Latin sētō, sētōn-.
Adapted from the Wiktionary entry seton (CC BY-SA 4.0).