Etymology 1
Feminine form of -ists.
Suffix
-iste
- Added to nouns to form feminine nouns denoting members/followers of a principle, religion, philosophy, lifestyle, or system of belief (usually named by words in -isms), or who has a certain profession or activity, just like its English cognate -ist.
- -ists (masculine counterpart of -iste)
- -isms (the corresponding profession / activity / system of belief)
Etymology 2
Apparently borrowed from Lithuanian -ystė, in words like karalỹstė (“kingdom”).
Suffix
-iste
- Used to form names of regions, areas, countries, etc. from the name of the their ruler: karalis “king” -> karaliste “kingdom.”