The Collaborative International Dictionary of English v.0.48:

Pernancy \Per"nan*cy\ (p[~e]r"nan*s[y^]), n. [OF. prenance, fr.
   prendre, prenre, penre, to take, L. prendere, prehendere.]
   (Law)
   A taking or reception, as the receiving of rents or tithes in
   kind, the receiving of profits. --Blackstone.
   [1913 Webster]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

PERNANCY. This word, which is derived from the French prendre, to take,
signifies a taking or receiving.