the.com/inner ear

means The fluid-filled inner chamber of the ear that handles both sound detection and your sense of balance and spatial orientation.

from Straightforward compound of 'inner' + 'ear' — no exotic roots here. 'Ear' traces back through Old English 'ēare' to a very old Indo-European root for 'ear' shared across many European languages. The anatomical sense of 'inner ear' as distinct from outer and middle ear is a matter of 19th-century scientific classification, once anatomists mapped out the cochlea and the vestibular system and realized this one small structure was doing two very different jobs at once.