Where does “pumpák” come from?

pumpák (Hungarian) comes from Hungarian -k, from Hungarian -ö-, from Hungarian -d, from Middle Welsh -nt — 3rd person plural verb ending.

Ancestry of “pumpák”, step by step

Step	Language	Word	Meaning
1	Hungarian	-k	-s, -es; Denotes the first-person singular...
2	Hungarian	-ö-	linking vowel
3	Hungarian	-d	your; Used in the second-person singular definite...
4	Middle Welsh	-nt	3rd person plural verb ending