Where does “trigeiniau” come from?
trigeiniau (Welsh) comes from Welsh trigain, from Welsh ugain, from Old Welsh uceint, from Proto-Brythonic ʉgėnt, from Proto-Celtic wikantī, from Proto-Indo-European h₁wih₁ḱm̥t, from Proto-Indo-European dwi(h₁)dḱm̥ti — two tens; two decades; twenty; two-ten.
trigeiniau (Welsh): sixties
Ancestry of “trigeiniau”, step by step