Green’s Dictionary of Slang

(US) baggy trousers, favoured by teenage gang members.

1992		Proper Dos ‘First Day of School’ 🎵 on Mexican Power [album] Had my jaina crease up my dickies, / Put a close hood on my neck, / So my other jaina wouldn’t see me hickies.
1997		(ref. to 1950s) G. Sikes 8 Ball Chicks (1998) 18: In the early 1950s, they created the look still seen today in parts of L.A.: chinos or cotton work pants called ‘dickies’ (requiring a ritual of ironing the trousers inside and out with starch so that the crease was so perfect the pants could stand up on their own).