The Collaborative International Dictionary of English v.0.48:

Fervency \Fer"ven*cy\, n. [Cf. OF. fervence. See Fervent.]
   The state of being fervent or warm; ardor; warmth of feeling
   or devotion; eagerness.
   [1913 Webster]

         When you pray, let it be with attention, with fervency,
         and with perseverance.                   --Wake.
   [1913 Webster]

WordNet (r) 3.0 (2006):

fervency
    n 1: feelings of great warmth and intensity; "he spoke with
         great ardor" [syn: ardor, ardour, fervor, fervour,
         fervency, fire, fervidness]