Webster's Revised Unabridged Dictionary · 1913

Pitapat

Pitapat , adverb

[An onomatopoetic reduplication of pat a light, quick blow.]

In a flutter; with palpitation or quick succession of beats. — L'Estrange
The fox's heart went pitapat. — Lowell

Pitapat , noun

A light, repeated sound; a pattering, as of the rain.
The pitapat of a pretty foot. — Dryden