Borrowed 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).