onychophosis

on·y·cho·pho·sis

(on'i-kō-fō'sis),
A growth of horny epithelium in the nail bed.
[onycho- + G. phōs, light, + -osis, condition]

onychophosis

(ŏn″ĭk-ō-fō′sĭs)
An accumulation of horny layers of epidermis under the toenail.