Meaning

noun a stretch of open water surrounded by ice (especially in Arctic seas)

originBorrowed from Russian полынья́ (polynʹjá, “polynya”) in the 1850s, from Middle Russian полыньѧ (polynʹja) (att. in 1639), from полыи (polyi, “open from above, uncovered; hollow”), whence also Russian полый (polyj, “hollow”), from Old East Slavic полъ (polŭ, “uncovered”), ultimately from Proto-Indo-European *pleh₂- (“flat”). The rare plural form polynyi is borrowed from Russian полыньи́ (polynʹí).

Etymology from Wiktionary, CC BY-SA 3.0