Green’s Dictionary of Slang

mocs n.

[abbr. SE moccasins]

(US) slip-on shoes.

[US]E. De Roo Go, Man, Go! 15: She took off her mocs and stood barefooted in his hands.
[US]E. Thompson Garden of Sand (1981) 172: A kid could stroll past [...] in Levis, mocs, and a skivvy shirt.