From Wikipedia:
A knish is a traditional Ashkenazi Jewish snack food consisting of a filling covered with dough that is typically baked or sometimes deep fried. Knishes are usually purchased from street vendors in urban areas with a large Jewish population, sometimes at a hot dog stand or from a butcher shop. It is still strongly associated with New York City, the New York City region, and New York City cuisine. It was made popular in North America by Ashkenazi Jewish refugees...
The food known as knish is delicious, a hot potato filled baked treat. My friends and I would buy this warmining treat during the typically cold Bronx winters. Yum!