From Latin 'cadere' (to fall) via Italian 'cadenza' — cadence is literally a falling, as the voice drops at a phrase's end.
A rhythmic flow of sounds or words; the rise and fall of the voice in speech.
From Old French 'cadence,' from Italian 'cadenza,' from Vulgar Latin *cadentia (a falling), from Latin 'cadere' (to fall), from PIE *ḱad- (to fall). Cadence is literally a falling — the voice falls at the end of a musical phrase or sentence. 'Cascade,' 'case,' 'cadaver,' 'accident,' and 'decadence