Where does “Zaleska” come from?

Zaleska (Polish) comes from Polish -a, from Old Polish -ą, from Proto-Slavic -a, from Proto-Indo-European -ōd.

Ancestry of “Zaleska”, step by step

Step	Language	Word	Meaning
1	Polish	-a	forms nominative feminine nouns
2	Old Polish	-ą	forms third person plural of verbs
3	Proto-Slavic	-a	id
4	Proto-Indo-European	-ōd	—