A common feminine suffix in Sindarin (SA/wen; PE17/190), a reduction of S. gwend “maiden” in compounds; see that entry for more examples.
Conceptual Development: In the Gnomish Lexicon of the 1910s the common female suffix was G. -win based on G. gwin “woman”, though Tolkien mentioned a variant -wein in Gnomish Lexicon Slips revising that document (PPE13/118). By the Noldorin of the 1930s, the usual suffix was -wen from N. gwenn “maiden”, and Tolkien seems to have stuck with it thereafter, as noted above.
_3rd pl. poss. suff. their.See also the paradigm of poss. suff. in PE17:46. Earlier -ent_. >> -ent