broacher

A broach, a spit (for cooking).

On five ſharp broachers rank'd, the roaſt they turn'd; [...]

One who broaches, opens, or utters; a first promoter or publisher.

broacher of a topic/argument etc.

Let not a Man therefore ſay, that the Scripture is not plain in thoſe things, in which we pretend it is, becauſe in thoſe very things, the Church of God hath Underſtood it one way, and Arius, Socinus, or ſome ſuch Broacher of Hereſy, another.