Where does “dyli” come from?

dyli (Welsh) comes from Welsh -i, from Old Welsh -im, from Proto-Brythonic *-iβ̃.

Ancestry of “dyli”, step by step

StepLanguageWordMeaning
1Welsh-iPluralisation suffix; Forms verbnouns from verb...
2Old Welsh-im—
3Proto-Brythonic*-iβ̃—
Every word from Proto-Brythonic *-iβ̃ →Every word from Welsh -i →Every word from Old Welsh -im →