Despite different etymologies estoner and entumir / estumir are semantically virtually indistinguishable, so that their orthographical similarity may well have led to confiusion of the different verbs.
v.a.
1to daze, stun:
(
s.xiii1/3; MS: c.1255
)
Tels quinze cols li paierai Que del primer l’esturnerai (l. estumerai)(P) 318
v.n.
1to be dumstruck, stunned:
(
s.xiii1; MS: s.xiv2
) Cum nus i entendium que nule tricherie n’i out [...], estoumes tuz em pais e attendiums nostre respons
549
p.p._as_a.
1numb:
(
c.1290; MS: 1307-25
)
Dunt avez la mein si estomie(M.E. comeled) Ki pur le freit ne purrez mie Dé deis fere la capinole (M.E. hant motile)602
[estumir] (s.xiii1/3)