Presumably derived from eye candy, which was first attested in 1984; the term has been attested in the USA since 1992.
arm candy (uncountable)
- (idiomatic) An attractive, seemingly romantic companion who accompanies a person in public simply so that one or both of the individuals can gain attention, enhance social status, or create an impression of sexual appeal.
2003 February 17, Jeffrey Ressner, “Shot on location”, in Time, archived from the original on 17 April 2016:
- Friends described her as always ready to serve as "arm candy"—that is, a pretty date—to industry players, in hopes of landing a role.