Where does “pleidleisio” come from?

pleidleisio (Welsh) comes from Welsh pleidlais, from Welsh plaid, from Scots plaid, from Scots ply.

pleidleisio (Welsh): to vote

Definitions

Step	Language	Word	Meaning
1	Welsh	pleidlais	a vote
2	Welsh	plaid	party
3	Scots	plaid	plaid
4	Scots	ply	—

pleidleisio — Etymology, Origin & Word History | Etymology Explorer