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" (cf. Greek lethe "forgetfulness, oblivion," Old Church Slavonic lajati "to lie in wait for"). Meaning "dormant" is from 1680s.
latent la·tent (lāt'nt)
adj.
Present or potential but not evident or active.
In a dormant or hidden stage, as an infection.
Undeveloped but capable of normal growth under the proper conditions.
Present in the unconscious mind but not consciously expressed.