Green’s Dictionary of Slang

pancho adj.

[the stereotypical Mexican name]

(US) pertaining to a Mexican or to Mexican lifestyle, fashions etc.

[US]C. Himes ‘Let Me at the Enemy’ in Coll. Stories (1990) 36: This George Brown was strictly an icky, drape-shaped in a fine brown zoot with a pancho conk slicker’n mine.