κοχλίας

Kochlias is the Greek word for a snail or snail shell. The anatomical cochlea — the spiral-shaped cavity in the inner ear — was named for its resemblance to a snail shell by Gabriele Falloppio (also known for the fallopian tubes) in 1561. The structure had been observed before, but Falloppio gave it the name that stuck. The cochlea is a coiled tube, about 9 millimeters across and making 2.5 turns, filled with fluid and lined with the organ of Corti — the structure that converts mechanical vibration into electrical nerve signals.

The cochlea is where hearing happens. Sound waves enter the ear canal, vibrate the eardrum, are amplified by the ossicles (the three tiny bones of the middle ear), and are transmitted to the fluid inside the cochlea. Different frequencies cause vibrations at different positions along the cochlear spiral — high frequencies near the base, low frequencies near the apex. This frequency mapping is called tonotopy, and it is the physical basis of pitch perception.

The word cochlea entered English from Latin in the 17th century. The Latin cochlea meant both 'snail' and 'spiral staircase' — Romans built cochlear staircases in towers and lighthouses. The architectural meaning and the biological meaning share the same spiral geometry. The ear's cochlea is a staircase for sound, spiraling from loud to quiet, from high to low.

Cochlear implants — electronic devices that bypass damaged cochlear hair cells to stimulate the auditory nerve directly — were developed in the 1960s and 1970s. The word cochlear, derived from a Greek word for snail, now names one of the most sophisticated pieces of medical technology in existence. The snail became the ear became the implant.