expression, noun
Refers to a painful, hardened area of skin on the foot, resembling a fish eye. Common in everyday health contexts.
足の裏に魚の目ができて痛い。
I have a corn on the sole of my foot and it hurts.
魚の目は圧力がかかるところにできやすい。
Corns tend to form where pressure is applied.
Search-only kanji form; not a practical spelling.
たこ (callus) is a broader, usually painless thickening of skin, while 魚の目 is a specific, often painful corn with a hard center.
From the resemblance of a corn's hard core to a fish's eye. The exact historical derivation is uncertain, but the term is widely used in modern Japanese.