I found this interesting little family tree of the silliness that is British Israelism and how it came into the COG.
It is from the Ephraimite Deception web site
By the 19th Century Anti-Semitism was rampant throughout most of the civilized world and the Jews of the diaspora had become a people rejected by most of the civilized world. Against this backdrop an Irish Minister of the 19th Century, John Wilson, published his essay entitled "Our Israelitish Origin" in 1840. Wilson attempted to provide empirical information that supported British- Israelism. His arguments suggested that similarities to English ways in certain elements in Hebrew language and social institutions were not merely coincidental.. British-Israel organizations formed during the 1870s on account of slow, but growing acceptanceof Wilson's teachings. The linguistic argument is still the principle argument used today to support this theory. Such concepts as Brit-Ish meaning "Covenant of Man" and the Gaelic word for name being "Shaim" have become cornerstones of the Brit-Israel concept. The reality is that most of these borrowed words can be traced to the documented Semitic origin of the Celtic people. A history which shows them to be Phoenician in origin. For more detail please read my page on The History of the European peoples.
Wilson's claims that the Irish were the residue of the lost tribes found it primary acceptance amongst the Millerites. The followers of a false prophet from New York named William Miller who proclaimed that "Jesus" would return on October 23, 1844 (Sukkoth) when he failed to appear he moved the date 6 months to approximently Pesach, 1845. After the failure of his prophecies the Millerites tended to fall apart but historically many of their adherents moved were instrumental in the forming of the Adventist Sects later in the 19th Century.
By the early 20th century these beliefs had migrated to America and tended to follow two distinct pathways to the modern day. First the Millerites had become the American Adventists which continue to this day as the sect known as Seventh Day Adventists. An offshoot of that sect developed in 1927 as the Worldwide Church of God under American Adventist Herbert W. Armstrong. In 1928, Howard B. Rand became the National Chairman of the Ango-Saxon Federation of America. Rand was a notorious Anti-Semite and by the 1940s he influenced Pastor Wesley Swift of Lancaster California to adopt a mixture of British Israelism and Racial Hatred that became the modern day Christian Identity Movement, the spiritual arm of the Ku Klux Klan. The Identity movement emphatically believes that the modern day Jews are of the House of Judah, while Anglo-Saxons are of the House of Israel. The movement maintains that only the Anglo-Saxons, of the House of Israel, have a covenant with God, thereby inducing pro-white attitudes.
Further information debunking British Israelism can be found here: Debunking British IsraelismSo the etymology of Anglo-Israelism traces the movement from one teacher using linguistic games in the early 19th century... through a false prophet to the formation of a strange legalistic sect (the Adventists) to a full blown cult (WWCOG) and its derivatives (COG) into modern day where we have seen that it produced as a sub-branch and anti-Semitic hate group
