Where does “pys” come from?

pys (Middle Welsh) comes from Proto-Brythonic *pɨs, from Latin pīsum, from Ancient Greek πίσον, from Ancient Greek πίσος — pea, pease, seed of "Pisum sativum".

Ancestry of “pys”, step by step

Step	Language	Word	Meaning
1	Proto-Brythonic	*pɨs	—
2	Latin	pīsum	pea, pease
3	Ancient Greek	πίσον	Quoted by comic poet Alexis; pea, pease, seed of...
4	Ancient Greek	πίσος	pea, pease, seed of "Pisum sativum"

Words derived from “pys”

pys
corbys
ffacbys
gwycbys

Every word from Ancient Greek πίσος →Every word from Ancient Greek πίσον →Every word from Latin pīsum →