A term of the people Gondolin (S/138), a combination that city’s name with the class-plural suffix -rim.
Conceptual Development: In the earliest Lost Tales, this term appeared as G. Gondothlim (LT2/155). It appeared as N. Gondothrim in The Etymologies from the 1930s (Ety/GOND), reflecting the change of G. -lim to N. -rim.
Gondolin + d (part of the original -ind ending) + rim (collective plural suffix)