Where does “Tyddewi” come from?

Tyddewi (Welsh) comes from Welsh tŷ, from Middle Welsh ty, from Proto-Brythonic tɨɣ, from Proto-Celtic tegos, from Proto-Indo-European (s)teg- — to cover; pole, stick, beam.

Ancestry of “Tyddewi”, step by step

Tyddewi traces back through two separate lines of ancestry.

via Welsh

StepLanguageWordMeaning
1Welshhouse
2Middle Welshty
3Proto-Brythonictɨɣhouse
4Proto-Celtictegoshouse, dwelling
5Proto-Indo-European(s)teg-to cover; pole, stick, beam

via Welsh dewi

StepLanguageWordMeaning
1WelshdewiSoft mutation of tewi
Every word from Proto-Indo-European (s)teg-Every word from Proto-Celtic tegosEvery word from Proto-Brythonic tɨɣ