Where does “pum ugain” come from?

pum ugain (Welsh) comes from Welsh pump, from Middle Welsh pymp, from Old Welsh pimp, from Proto-Brythonic pɨmp, from Proto-Celtic kʷenkʷe, from Proto-Indo-European pénkʷe — five.

Ancestry of “pum ugain”, step by step

pum ugain traces back through two separate lines of ancestry.

via Welsh pump

StepLanguageWordMeaning
1Welshpumpfive
2Middle Welshpymp
3Old Welshpimp
4Proto-Brythonicpɨmpfive
5Proto-Celtickʷenkʷefive
6Proto-Indo-Europeanpénkʷefive

via Welsh ugain

StepLanguageWordMeaning
1Welshugaintwenty; score
2Old Welshuceint
3Proto-Brythonicʉgėnt
4Proto-Celticwikantītwenty
5Proto-Indo-Europeanh₁wih₁ḱm̥t
6Proto-Indo-Europeandwi(h₁)dḱm̥titwo tens; two decades; twenty; two-ten
Every word from Proto-Indo-European pénkʷeEvery word from Proto-Celtic kʷenkʷeEvery word from Proto-Brythonic pɨmp