The FEW (pertinere 8,283b) notes the forms pertenemen (1245), pertenemeint (1197), pertenement (1624) and partenemen, all of which are attested only in the south of France. The word is only attested in English from the late seventeenth century. It's use in this text is unexpected but the word may represent an aphetic form of apurtenement which was more widely used during the period.