Footprints of the Red Men: Indian Geographical Names — Passage 65 (part 6)
[Edward Manning Ruttenber (1906)] The tract was known for years as "The end place." Sankapogh, Indian deed to Van Cortlandt, 1683--Sinkapogh, Songepogh, Tongapogh--is given as the name of a small stream flowing to the Hudson south of the stream called Assinapink, locally now known as Swamp Kill and Snake-hole Creek. The stream is the outlet of a pool or spring which forms a marsh at or near the foot of precipitous rocks. Probably an equivalent of Natick _Sonkippog,_ "Cool water." Poplopen's Creek, now so written, the name of the stream flowing to the Hudson between the sites of the Revolutionary forts Clinton and Montgomery, south of West Point, and also the name of one of the ponds of which the stream is the outlet, seems to be from English _Pop-looping_ (Dutch _Loopen_), and to describe the stream as flowing out quickly--_Pop_, "To issue forth with a quick, sudden movement"; _Looping_,