An ear was an sensory organ associated with hearing.
While visiting the Quadrant in 1987, Chris Cwej got an earring in his right ear. At the time in England, this was an indication that the wearer was gay, but he was initially unaware of the significance. (PROSE: Damaged Goods)
When the War Doctor regenerated he hoped his ears would be less conspicuous. (TV: The Day of the Doctor) The Ninth Doctor referred to the size of his ears when he met Rose Tyler. (TV: Rose) Mickey Smith once refered to him as "big ears". (TV: Boom Town)