Lewis & Short

fornācŭla, ae, f. dim. [fornax], a little furnace or oven.

  1. I. Lit., Juv. 10, 82; Vitr. 7, 10, 1; Front. Ep. ad M. Caes. 1, 2 ed. Mai.
  2. * II. Trop., a kindler, exciter: hic totius calumniae fornacula, App. Mag. p. 321, 32.