"Place where water passes beyond." (information from Isaac Harris, published in Vernon News, July 18, 1918); compare with: "Derived from the Okanagan dialect of the Salish tribe, the word Pen-tak-tin meaning 'a place of permanent abode where waters pass by'." (50th Anniversary booklet of Penticton, 1958)
From the Indian name ''Pente-hik-ton'', "ever" or "forever", referring to the constant, steady flow of the Okanagan River out of the lake.... applied by the Indians to the locality at the outlet of the lake, meaning that the stream ran on ever, or forever, in contrast to other streams which dried up during the summer (6th Report of the Okanagan Historical Society); compare with: "Derives from the Okanagan word Sin-peen-tick-tin, loosely translatable as 'permanent place'." (c1980 advice from Randy Bouchard, BC Indian Language Project).