Adopted in the 10th Report of the Geographic Board of Canada 30 June 1911, as a long-established name and as long-labelled on maps. Re-approved 28 April 1936 on BC map 3G.

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

Labelled "Columetza Lake" on Arrowsmith's 1859 map.
Labelled "William Lake" on Geographical Journal map, 1861.
"...Williams's Lake (also called Columetza)..." (from an article entitled "To Cariboo and back" by W. Champness, published in the periodical "The Leisure Hour", 1865, v14, p232).
"...the lac de Colum-en-eet-sa or William's Lake as it is now called, is another beautiful lake of rather smaller dimensions." (from an unpublished c1867 manuscript, p.13, by HBC surveyor and explorer A.C.Anderson (Provincial Archives E-C-An3.3).

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

"...No story of Williams Lake would be complete without at least brief mention of William Pinchbeck, after whom the lake in the beautiful San Jose Valley would have been called had not 'Squatter' Williams, an American, preceded him..." (Williams Lake Tribune, 27 May 1948). See Williams Lake (City) for another version.

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