Where does “tair ar bymtheg” come from?

tair ar bymtheg (Welsh) comes from Welsh ar, from Middle Welsh ar, from Proto-Brythonic ar, from Proto-Celtic aros, from Proto-Indo-European h₂erh₃-o-, from Proto-Indo-European h₂erh₃-, from Proto-Indo-European h₁er- — earth.

Ancestry of “tair ar bymtheg”, step by step

tair ar bymtheg traces back through 3 separate lines of ancestry.

via Welsh ar

StepLanguageWordMeaning
1Welsharon; about to
2Middle Welsharon, upon; over, of; he/she who, whoever
3Proto-Brythonicarin front of; ploughing, ploughed land
4Proto-Celticarosploughing, ploughed land
5Proto-Indo-Europeanh₂erh₃-o-ploughing
6Proto-Indo-Europeanh₂erh₃-to plough
7Proto-Indo-Europeanh₁er-earth

via Welsh tair

StepLanguageWordMeaning
1Welshtairfeminine of tri; three
2Proto-Celtictisres—
3Proto-Indo-Europeantisresfeminine nominative/vocative of *tréyes
4Proto-Indo-Europeantrisres—
5Proto-Indo-Europeantréyesthree

via Welsh pymtheg

StepLanguageWordMeaning
1Welshpymthegfifteen
Every word from Proto-Indo-European h₁er- →Every word from Proto-Indo-European h₂erh₃- →Every word from Proto-Indo-European h₂erh₃-o- →