Where does “pléidh” come from?

pléidh (Middle Irish) comes from Anglo-Norman plai, from Medieval Latin placitum, from Latin placitus, from Latin placeō.

Ancestry of “pléidh”, step by step

Step	Language	Word	Meaning
1	Anglo-Norman	plai	lawsuit
2	Medieval Latin	placitum	a decree, sentence, suit, plea, etc.,...
3	Latin	placitus	pleasing, agreeable, acceptable, agreed upon
4	Latin	placeō	—

pléidh — Etymology, Origin & Word History | Etymology Explorer