When the wind stirred the branches a little fire of drops sounded "clop, clop!"
It seemed to shout to Joanna as she came to it clop, clop along the road.
The creak of saddle leather and the clop clop of her horses hoofs were all the sounds that disturbed the stillness.
1901, echoic of the sound of boots or hoofs on the ground. Related: Clopped; clopping.