Why is the ninth month called September?
masc. proper name, from the family name, from the region of the Clyde River in Scotland (see Clydesdale). Most popular in U.S. for boys c.1890-1910, falling off rapidly thereafter, hence probably its use in 1940s teenager slang for "a square, one not versed in popular music or culture."
A person who does not appreciate the current music, culture, etc; square (1940s+ Students)