Osoyoos Lake adopted in the 18th Report of the Geographic Board of Canada, 31 March 1924, as labelled on Trutch's 1866 & 1871 maps of BC, et seq.

Source: BC place name cards, or correspondence to/from BC's Chief Geographer or BC Geographical Names Office

Labelled "Forks Lake" on Arrowsmith's 1859 map; labelled "Osoyoos" on a map of 1859 [title not cited]. This is an Indian word with over a dozen spellings. Judge Hayes arrived in the area in 1861; in his letters from 1861-71 he used the spelling "soyoos" (October 1961 advice from Provincial Archives).

Source: Provincial Archives of BC "Place Names File" compiled 1945-1950 by A.G. Harvey from various sources, with subsequent additions

From an Indigenous language, "soo-yoos" - "where two lakes come together," "a shallow crossing," or "a sheet of water divided in two by a narrow extension of land from opposite sides" - referring to the shape of the lake. Laing tells of a legend that when Honourable Peter O'Reilly, an Irishman who was magistrate at Hope (appointed 1858), visited the district he thought the Indigenous name ought to be dignified by adding an "O". However, Mrs. R. B. White, Penticton, daughter of Judge Haynes, thinks the "O" may have been added by her father. Indigenous people say the "O" was added prior to white settlement. (12th Report, Okanagan Historical Society, 1948, citing BCHQ, 4:195; Gosnell, 348; Laing, "Names", 13; Parham, 39; Mrs. R. B. White).

Source: BC place name cards, or correspondence to/from BC's Chief Geographer or BC Geographical Names Office

Same origin as Tsuius Narrows (Mabel Lake) where that lake is almost cut in two.

Source: BC place name cards, or correspondence to/from BC's Chief Geographer or BC Geographical Names Office