E. Randol Schoenberg
My understanding is that the legends of Sephardic roots for Latvian and
Lithuanian Jews are of recent origin, likely late 19th century, as part
of the fad of inventing claims of Sephardic origin around that time. I
have not seen a single case with evidence before that time.
See also John M. Efron, German Jewry and the Allure of the Sephardic
Los Angeles, CA