bozo

Attested since the 1910s in American English, of uncertain origin. The term may derive from Spanish bozal, a term originally for a recently-imported slave and then "someone who speaks (Spanish) poorly". The term is older than Bozo the Clown, introduced in 1946. It is used as an insult in the 1931 Marx Brothers movie Monkey Business (1931 film). Derivation of the term from French bouseux /bu.zø/, a derogative term for a farmer equivalent to "bumpkin", is phonologically unlikely. Another possibility is Japanese 坊主 (bōzu) in its meaning of "young man", which can be derogatory, depending on the context.

来源：wiktionary