- impenetrable (adj.)
[impenetrable 词源字典]
- mid-15c., from Middle French impenetrable, from Latin impenetrabilis "that cannot be penetrated," from assimilated form of in- "not, opposite of" (see in- (1)) + penetrabilis "penetrable" (see penetrate). Related: Impenetrably; impenetrability.[impenetrable etymology, impenetrable origin, 英语词源]