קווייט
ETYMOLOGY
Beider suggests the word may have been borrowed from the dialect of Polesia, where the root vowel was the diphthong {ie} - borrowed into Yiddish as {ej}. Or perhaps the word is much older and is from the East Cnaanic substrate - from the Slavic language originally spoken by Jews in the Grand Dutch of Lithuania before they shifted to Yiddish (by the 17th c.).
Ukrainian квiт 'flower'.
{Beider 2015: 440-1}
Old Polish kwiet (modern Polish kwiat); Old Czech květ; cf. Ukrainian цвіт; Russian цвет;
Proto-Balto-Slavic ✱kwaitas, from PIE ✱ḱuoit-o-, from ✱ḱueit- 'white'
{Derksen 2008: 258}
Herzog writes that CY had the form kjut from Polish kwiat, probably because the word entered Yiddish from a Polish dialect where the vowel was /o/, which was then subject to the regular shift o > u in SY. {How widespread was this form?}