Kirke grabbed my hand and squeezed it chummily, and I smiled at him.
She held out a slender shapely hand and Connie took it quickly, chummily, and the two girls turned toward the door.
1874, from chum (n.1) + -y (2). Related: Chumminess. Previously it was a noun, a common name for a chimney sweep, as a corruption of chinmey.
Very friendly; buddy-buddy, palsy-walsy (1880s+)