perfide
Found Perfide with different capitalization.
Perfide adverb, neuter vocative singular, masculine vocative singular, masculine vocative singular of perfidus
perfĭdē, adv., v. perfidus fin.
perfidē, Adv. (perfidus), treulos, pater crudeliter exponens, perfide recipiens, Sen. contr. 9, 3 (26). § 11: perf. rumpere pactum, Gell. 20, 1, 54: p. agere, Tryphon. dig. 26, 7, 55. § 1: quod perf. gestum est, Ulp. dig. 44, 4, 4. § 13.
perfĭdē (16) (perfidus), perfidement, traîtreusement : Sen. Rhet. Contr. 9, 3, 11 ; Gell. 20, 1, 54.