Seems to be a type of wind, quite distinct from the more common term of ‘cat’s paw’ which refers to someone used to do someone else’s dirty work.  In Arthur Ransome, however, I found: ‘There was very little wind, though now and again a catspaw hurrying from the south helped them on their way.’  As it seemed to ripple the surface of the water, I imagine a cat delicately pawing the surface.
Source: Arthur Ransome, Swallows and Amazons (London: Vintage, 2015 (1930)), p. 497
