pirogi (n.)

also pierogi, pirog, "Polish ravioli; small dumpling made of dough stuffed with potato, cheese, etc.," 1854, via Yiddish, from Russian, plural of pirog "pie," perhaps borrowed from the Turkic language of the Kazan Tatars (compare Turkish borek). But Watkins and Ayto say from Old Church Slavonic pirŭ "feast," from PIE root *po(i)- "to drink." The plural form has become singular in English.