"a throb, a beat," early 14c., from Old French pous, pulse (late 12c., Modern French pouls) and directly from Latin pulsus (in pulsus venarum "beating from the blood in the veins"), past participle of pellere "to push, drive," from PIE root *pel- (5) "to thrust, strike, drive." Extended usages from 16c. Figurative use for "life, vitality, essential energy" is from 1530s.