adult (adj.)youdaoicibaDictYouDict[adult 词源字典]
1530s (but not common until mid-17c.), from Latin adultus "grown up, mature, adult, ripe," past participle of adolescere "grow up, mature" (see adolescent). As a euphemism for "pornographic," it dates to 1958 and does no honor to the word.[adult etymology, adult origin, 英语词源]
adult (n.)youdaoicibaDictYouDict
"adult person," 1650s, from adult (adj.).