Where does “kezby” come from?

kezby (Polish) comes from Polish -ż, from Proto-Slavic že, from Proto-Balto-Slavic ge, from Proto-Indo-European ǵʰe — Postpositional intensifying particle: indeed, at any rate, in fact.

Ancestry of “kezby”, step by step

Step	Language	Word	Meaning
1	Polish	-ż	appended to create an emphatic form
2	Proto-Slavic	že	so that, since; "emphatic enclitic"
3	Proto-Balto-Slavic	ge	—
4	Proto-Indo-European	ǵʰe	Postpositional intensifying particle: indeed, at any rate, in fact

Every word from Proto-Indo-European ǵʰe →Every word from Polish -ż →Every word from Proto-Balto-Slavic ge →