unfledged (adj.)youdaoicibaDictYouDict[unfledged 词源字典]
c. 1600, of persons, "immature, not experienced," from un- (1) "not" + past participle of fledge (v.). Literal sense of "not yet covered in feathers" is recorded from 1610s.[unfledged etymology, unfledged origin, 英语词源]