fem. proper name, from Greek aletheia "truth, truthfulness," from alethes "true," literally "not concealing," from privative prefix a- "not" (see a- (3)) + lēthē "forgetfulness, oblivion, concealment," from PIE root *ladh- "be hidden" (see latent).
Greek also had an alpha copulativum, a- or ha-, expressing union or likeness, which is the a- expressing "together" in acolyte, acoustic, Adelphi, etc. It is from PIE root *sem- (1) "one; as one, together with."
mid-15c., "concealed, secret," from Latin latentem (nominative latens) "lying hid, concealed, secret, unknown," present participle of latere "lie hidden, lurk, be concealed," from PIE *late-, suffixed form of root *lādh- "to be hidden" (source also of Greek lēthē "forgetfulness, oblivion," lēthargos "forgetful," lathre "secretly, by stealth," lathrios "stealthy," lanthanein "to be hidden;" Old Church Slavonic lajati "to lie in wait for"). Meaning "dormant, undeveloped" is from 1680s, originally in medicine.
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Harper, D. (n.d.). Etymology of Alethea. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/Alethea