胼胝[tako] callus
ペン胼胝[pendako] callus on one's middle finger (from writing)
耳に胼胝ができる[miminitakogadekiru] to be told or made to hear something so often that you (metaphorically) get calluses on your ears

胼胝体[benchitai] corpus callosum
座り胼胝[suwaridako] calluses (on one's ankles, insteps, etc.) caused by sitting seiza