Maybe lanya-¹ v. “to bound, enclose, separate from, mark the limit of” -> *etelanya "separate out, outlaw, excommunicate" -> *etelanyare "excommunication" ?
eldamo.org - Eldamo : Quenya : lanya-¹

Or if you want to go more literal you might look at the root KAN, verb kanya-

In Hungarian one way to say "excommunicate" is kiátkoz which means "curse out" [i.e. out of the Chuch] which would be sg like *ehtúta- in Quenya.

?etomat-
https://eldamo.org/content/words/word-3391372331.html
eldamo.org - Eldamo : Early Primitive Elvish : ŋwa·mat

Excommunication has nothing to do with not eating together. heeeheee

+James Coish of course, but this entry suggests Tolkien once upon a time thought of community as a group of people having meal together, and that is not totally untrue if we think of communion as a bread and wine sacrament.

+Remy Corbin actually the word companion means someone eating bread with you