Green’s Dictionary of Slang

josh adj.

amusing.

1913		Van Loan ‘The Bachelor Benedict’ in Lucky Seventh (2004) 231: ‘Here’s a good josh story,’ said the editors. ‘Mace Henshaw’s sister-in-law [...] runs away with his star pitcher.’.
1999		Indep. Rev. 9 Nov. 8: I thought he’d at least say something joshy.