latent (adj.) Look up latent at Dictionary.com
mid-15c., "concealed, secret," from Latin latentem (nominative latens) "lying hid, secret, unknown," present participle of latere "to lie hidden," from PIE *laidh-, from root *la- "to be hidden" (cognates: Greek lethe "forgetfulness, oblivion," Old Church Slavonic lajati "to lie in wait for"). Meaning "dormant" is from 1680s.