Semiamu Bay adopted 31 March 1924 as appears on Reference Map 10 "Port Moody - Sectional Map" (1913) and as listed in 1924 Gazeteer. Previously labeled as Semiamo Bay on Reference Map 2B "New Westminister and Yale" (1913) and Semiamoo Bay on International Boundary Survey Sheet #2 (date not cited). Spelling changed 6 October 1949 to Semiahmoo Bay to reflect consistency with local usage (F.1. 34 #1).

Source: BC place name cards & correspondence, and/or research by BC Chief Geographer & Geographical Names Office staff.

"The Semiahmoo peoples are a coast Salish group closely related to the Lummi and Samish First Nations who live [south] of the international border. They once occupied a larger area that included the shores of Mud and Boundary bays and extended to the [south] side of Birch Bay in US territory. The word is reported to mean 'half moon' - presumably a reference to the curve of the shoreline - but this translation is dubious... Many variations of the name are recorded, including Semiamo, Semiamu and Semiahoo." (p. 536).

Source: Scott, Andrew; "The Encyclopedia of Raincoast Place Names"; Harbour Publishing, Madeira Park, 2009.

"Named from the Semiamu [nation], of the Songish group of the Salish [peoples], residing here and on the coast of northern Washington, over the [border]. In 1843 they numbered 300, while in 1911 there were 40 living on the Canadian side.

Source: Nelson, Denys; "Place Names of the Delta of the Fraser River"; 1927, unpublished manuscript held in the Provincial Archives

"Named after the 'Semiahmoo' [Nation], members of the Songhish group of the Salish linguistic [family], who reside here on the coast of Northern Washington over the line. They also dwell along the shores of the Straits of Juan de Fuca, and the island of that name as well. The bay was called Birch Bay in the early days."

Source: BC place name cards & correspondence, and/or research by BC Chief Geographer & Geographical Names Office staff.