Green’s Dictionary of Slang

1. a Pomeranian dog.

1904		Outing (N.Y.) Feb. 484/2: Collies and ‘poms’ in America have hardly maintained their status because of this coat trouble.
1914		E. Wittmann ‘Clipped Words’ in DN IV:ii 134: Pom, from Pomeranian dog.
1920		O.O. McIntyre Bits of New York Life 14 Dec. [synd. col.] The girl held a leash which was fastened to a pom.
1938		D. Runyon ‘Lillian’ in Runyon on Broadway (1954) 282: The pooches [...] are mainly nothing but Chows, and Pekes, and Poms.
1996		D. Healy Bend for Home 31: The pom called Croney walks the wall and sits on the pier of the gate.

2. see pommie n.