Where does “куплений” come from?

куплений (Ukrainian) comes from Ukrainian купити, from Proto-Slavic kupiti, from Proto-Germanic kaupōną, from Proto-Germanic kaupô, from Latin caupo, from Proto-Indo-European kaup-.

Ancestry of “куплений”, step by step

Step	Language	Word	Meaning
1	Ukrainian	купити	to buy, to purchase
2	Proto-Slavic	kupiti	to pile, to gather in one place; to buy, to trade
3	Proto-Germanic	kaupōną	to buy; trade
4	Proto-Germanic	kaupô	innkeeper; merchant
5	Latin	caupo	Tradesman; Innkeeper, shopkeeper
6	Proto-Indo-European	kaup-	—

Every word from Proto-Indo-European kaup- →Every word from Latin caupo →Every word from Proto-Germanic kaupô →