Type Word Usage Old Welsh Meaning & History Old Welsh word meaning "valley" [1]. Related ItemsFamily Tree·Details Other Languages & Culturesglendos(Old Celtic) glenn(Old Irish) Given Name DescendantsGlendower, Glenice, Glennis, Glenys, Glyn, Glyndwr, Glynis, Glynn(Welsh) Surname DescendantGlynn(Welsh) Sources & References Matasović, Ranko. Etymological Dictionary of Proto-Celtic. Brill, 2009, page 160.