What does Sinclair mean?
Sinclair \s(i)-nc-lair, sin-clair\ as a boys' name is pronounced sin-KLARE. It is of English origin, and the meaning of Sinclair is "from Saint-Clair". Based on the name of a place in northern France. See also Santana and Seymour. Authors Sinclair Lewis, Upton Sinclair.
Sinclair is an unusual given name for males but a very prominent last name for all people (#1239 out of 150436, Top 1%). (2000 U.S. Census)
Displayed below is an analysis of the usage of the boy name Sinclair and affiliated names. Popular variation forms of Sinclair (#unlisted) are Santana (#887 the previous year) and Seymour. Adoption of these boy names was at its apex during the years 1920-1929 (usage of 0.3885%) and has become much lower since (usage 0.0565%, down 85.5%), with the form Seymour becoming less in vogue. (Top 1000 Baby Names Records, 2014)