Green’s Dictionary of Slang

1. (orig. US black) an unsophisticated person, a provincial, a yokel.

1950		C.W. Gordon High School 114: Positive rated persons [...] are ‘hep’ [...] and ‘george’ [...] negatively rated ‘fruits’ and ‘clydes.’.
1968		‘Hy Lit’ Hy Lit’s Unbelievable Dict. of Hip Words 9: clyde – The ultimate handle for the ultimate in squareness.
1997		(con. early 1950s) Space Ghost ep. 50 (Cartoon Channel) [TV script] My brother’s a total Clyde, baby. Uptight!
2003		posting at cyclingforums.com 🌐 Ya don’t need special custom built heavy duty wheels unless you are a total clyde.

2. a general term of address.

1962		Mad mag. July 10: Simple, Clyde, she was gettin’ too big for her rubber pants.
1992		UGK ‘Trill Ass Nigga’ 🎵 And I’m about to get some shit on my toes / And I’ma keep on doin it Clyde.