variable (adj.)youdaoicibaDictYouDict[variable 词源字典]
late 14c., of persons, "apt to change, fickle," from Old French variable "various, changeable, fickle," from Late Latin variabilis "changeable," from variare "to change" (see vary). Of weather, seasons, etc., attested from late 15c.; of stars, from 1788.[variable etymology, variable origin, 英语词源]
variable (n.)youdaoicibaDictYouDict
"quantity that can vary in value," 1816, from variable (adj.) in mathematical sense of "quantitatively indeterminate" (1710). Related: Variably; variability.