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).