Green’s Dictionary of Slang

chow phr.

goodbye (cf. ciao phr.).

1961		H. Ellison Rockabilly (1963) 78: At the door he paused [...] and said, ‘Chaow!’ Then he was gone.
1976		D. Ireland Glass Canoe (1982) 190: He grinned at me and grabbed a bag from the back seat of her car and said Chow and off.
1986		Eble Campus Sl. Mar. 2: ciao! – salutation; or an action to gain attention: Chow, Babes!
1989		P. Munro Sl. U.
2003		posting at www.fanfiction.net 15 Aug. 🌐 Anyhoo again, I’ll be back to upadate this thing later. Chow Babes.

In phrases

chow for now

(US campus) goodbye.

1991		Eble Campus Sl. Fall.
1996		Eble Sl. and Sociability 100: Many college slang farewells are foreign terms or deliberate alterations of foreign terms:[...] chow for now.
2004		deanscyberspace.wordpress.com 29 Apr. [blog] Ahh, I guess everyone has a lousy, or boring day. After all, nothing is perfect, right? Ahhh, ok. Chow for now.