cognĭtor (noun M) : cognosco, a judic. t. t.
* Lit., one who has made himself familiar with a case in law; hence
* A witness, who testifies that he knows a person, a voucher, Cic. Verr. 2, 5, 65, § 167 sq.; cf. id. ib. § 168; 2, 1, 5, § 13.
* In gen., a defender, protector: hoc (Caesare) auctore et cognitore hujusce sententiae,Cic. Cat. 4, 5, 9; Auct. Harusp. 21, 45; Liv. 39, 5, 2; Hor. S. 2, 5, 38 al.: Liber dithyramborum cognitor,Front. Eloqu. p. 217.

s. TLL