1880, from Latinized form of Greek ephebikos "of or for an ephebe," from ephebos "one arrived at puberty, one of age 18-20," from epi "upon" (see epi-) + hēbē "early manhood," from PIE *yegw-a- "power, youth, strength." In classical Athens, a youth of 18 underwent his dokimasia, had his hair cut off, and was enrolled as a citizen. His chief occupation for the next two years was garrison duty.
<a href="https://www.etymonline.com/word/ephebe">Etymology of ephebe by etymonline</a>
Harper, D. (n.d.). Etymology of ephebe. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/ephebe