Lewis & Short

pignĕror, ātus, 1, v. dep. a. [id.]. Lit., to take as a pledge; hence, trop.,

  1. I. To make one’s own, to appropriate (rare but class.): Mars ipse ex acie fortissimum quemque pignerari solet, Cic. Phil. 14, 12, 32: maximas ingenii, consilii partes sibi ad utilitatem suam, id. Rep. 1, 4, 8 (cited in Non. 477, 31 sq.): fidem militum praemio pigneratus, Suet. Claud. 10.
  2. II. To accept as certain: quod das mihi, pigneror, omen, Ov. M. 7, 621.