Origins
The word 'sound,' meaning audible vibration, entered English in the thirteenth century from Anglo-Frβββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββench 'soun' and Old French 'son' (sound, noise, musical note), from Latin 'sonus' (sound, noise, tone), from PIE *swenhβ- (to sound, to resonate). At the outset that English has three entirely unrelated words spelled 'sound': this one (noise, from Latin 'sonus'), 'sound' meaning healthy or solid (from Old English 'gesund,' cognate with German 'gesund'), and 'sound' meaning a body of water or to measure depth (from Old English 'sund,' a swimming, a strait, and Old French 'sonder,' to plumb). These are three different words that have converged in spelling by coincidence.
The most curious feature of the acoustic 'sound' is its final '-d,' which is unetymological β it was not present in Latin 'sonus,' Old French 'son,' or the earliest Middle English borrowing 'soun.' The parasitic '-d' was added during the fourteenth and fifteenth centuries, probably by analogy with words like 'ground,' 'bound,' and 'round,' where the final '-d' is etymologically legitimate. This is a well-documented phenomenon in English historical phonology: unetymological consonants are sometimes added to borrowed words to make them feel more 'English.' The same process added a '-d' to 'expound' (from Latin 'exponere') and a '-b' to 'crumb' (Old English 'cruma').
The Latin root 'sonus' was extraordinarily productive, and its derivatives pervade English musical and scientific vocabulary. 'Sonic' (relating to sound) is a twentieth-century coinage from Latin 'sonus' + the suffix '-ic.' 'Sonata' (from Italian 'sonare,' to sound) means 'a thing sounded' β as opposed to 'cantata' ('a thing sung'). 'Sonnet' (from Italian 'sonetto,' a little sound or song) is a poem-form named for its musical quality. 'Resonance' (from Latin 're-' + 'sonΔre,' to sound back) is the amplification produced when vibrations reinforce each other. 'Consonant' (from Latin 'con-' + 'sonΔre,' to sound together) was originally a musical term meaning 'harmonizing' before it became a phonetic term. 'Dissonance' (sounding apart) is the opposite. 'Unison' (from Latin 'Ε«ni-sonus,' one-sound) means voices or instruments producing the same pitch.
Proto-Indo-European Roots
The PIE root *swenhβ- also produced Sanskrit 'svana' (sound, noise) and 'svanati' (it sounds), confirming the antiquity of the root. The Latin derivative 'sonΔre' (to sound) is the ancestor of modern French 'sonner' (to ring), Italian 'suonare' (to play an instrument), and Spanish 'sonar' (to sound, to ring). The acronym SONAR (Sound Navigation and Ranging) uses the Latin root with deliberate etymological awareness.
The verb use of 'sound' (to make a noise, to emit sound) dates from the thirteenth century. The figurative use β 'that sounds right,' 'it sounds like a good idea' β where 'sound' means 'seem' or 'appear,' emerged in the sixteenth century, extending the auditory metaphor to general impression.