late 14c., "flow of rhythm in prose or verse," from Middle French cadence, from Old Italian cadenza "conclusion of a movement in music," literally "a falling," from Vulgar Latin *cadentia, from neuter plural of Latin cadens, present participle of cadere "to fall," from PIE root *kad- "to fall." A doublet of chance (n.).
The notion is of a "fall" in the voice in reading aloud or speaking, as at the end of a sentence, also the rising and falling in modulation of tones in reciting. Later (1590s) extended to music, in reference to a sequence of chords expressing conclusion at the end of a phrase and resolving to the key in which the piece was written. Also the measure or beat of any rhythmic movement (c. 1600). In 16c., sometimes used literally for "an act of falling." Related: Cadential.