Where does “pla” come from?

pla (Middle Welsh) comes from Proto-Brythonic *plaɣ, from Vulgar Latin *plăga, from Latin plāga, from Latin plagius, from Ancient Greek πλάγιος, from Ancient Greek -ῐος, from Proto-Indo-European -yós — Creates adjectives from noun or verb stems.

Ancestry of “pla”, step by step

Step	Language	Word	Meaning
1	Proto-Brythonic	*plaɣ	—
2	Vulgar Latin	*plăga	—
3	Latin	plāga	plague, misfortune
4	Latin	plagius	—
5	Ancient Greek	πλάγιος	placed sideways, slanting, aslant
6	Ancient Greek	-ῐος	belonging to; of”, “belonging to”, “pertaining to
7	Proto-Indo-European	-yós	Creates adjectives from noun or verb stems

Words derived from “pla”

Every word from Proto-Indo-European -yós →Every word from Ancient Greek -ῐος →Every word from Ancient Greek πλάγιος →