The use of an a- prefix (instead of en- (see enparkement) has its verbal equivalent in the Latin verb apparcare (DMLBS 103a), but otherwise does not seem to be attested.
(
1280-1307; MS: s.xiv1/4
)
[...] Ke forestes et boys saunz enparkement (var.
(B: s.xiv2/4) aparkement
) Serrait a clers et lays perpetuelement
i 468 (var.)
aparkement (s.xiv2/4)