treble: [14] Treble and triple [15] come from the same ultimate source: Latin triplus ‘threefold’. This in turn was borrowed from Greek triplous, a compound adjective formed from tri- ‘three’ and the base *pl- ‘fold’ (which lies behind English ply and is related to English fold). Triplus passed into Old French, where it split into two: treble and triple. Both were taken over into English (the former has now died out in French). The application of treble to the highest part in music, equivalent to soprano, which dates from the 14th century, probably comes from the notion of its being the ‘third’ part, above bass and alto. => fold, ply, three, triple
treble (adj.)
"three times, triple," c. 1300, from Old French treble (12c.), from Latin triplus "threefold" (see triple). Related: Trebly.
treble (v.)
"to multiply by three," early 14c., from Old French trebler, from treble "triple" (see treble (adj.)). Related: Trebled; trebling.
treble (n.)
"highest part in music, soprano," mid-14c., from Anglo-French treble, Old French treble "a third part," noun use of adjective (see treble (adj.)). In early contrapuntal music, the chief melody was in the tenor, and the treble was the "third" part above it (after the alto).
