Green’s Dictionary of Slang

1. an excellent or admirable person or thing.

1895		S. Crane Red Badge of Courage (1964) 134: That’s Flemin’, an’ he’s a jim-hickey.
1904		G.V. Hobart [title] Jim Hickey.

2. as the equivalent of hell of a, a under hell n.

1907

J. Masefield Tarpaulin Muster 131: There was a jim hickey of a stink raised.