callus (n.)youdaoicibaDictYouDict[callus 词源字典]
"hardened skin," 1560s, from Latin callus, variant of callum "hard skin," related to callere "be hard," from PIE root *kal- (3) "hard" (cognates: Sanskrit kalika "bud," Old Irish calath "hard," Old Church Slavonic kaliti "to cool, harden").[callus etymology, callus origin, 英语词源]