means Striking something repeatedly with heavy blows, or throbbing with a strong, insistent beat — as a heart, headache, or set of fists might do.

from From Old English 'pūnian,' meaning to beat, bruise, or crush, the same verb that gives us 'pound' the action (distinct from 'pound' the weight, which traces to Latin 'pondo'). The intrusive 'd' on the end crept in during the Middle English period, the way it did in 'sound' and 'gown' — a wandering consonant English keeps acquiring. So a pestle pounding spice and a heart pounding in your chest share one ancient root: the simple, physical act of striking again and again.