Maps show there has always been a traffic circle in this spot since the park opened, and the apartment buildings on Bartel-Pritchard were built along the gentle curves of the circle. The square was named in 1923 for Emil Bartel and William Pritchard, two young Brooklyn natives who were killed in combat in World War I. Bartel was a Windsor Terrace native while Pritchard was from Bushwick. The polished granite memorial to Windsor Terracers killed in combat was placed here in 1965.
A side note: most major NYC intersections are called “squares” even though they take many shapes: circles, triangles, rhomboids, or other multisided figures. In Britain, many traffic circles are called “roundabouts” and, while in NYC we do have traffic circles, traffic is controlled by stoplights, as it is here. Technically, a “roundabout” has no traffic lights at all; NYC did not have any of these until one was installed in Longview, in the Bronx, at Intervale Avenue and Dawson Street.