ignorant

1325–75; Middle English ignora(u)nt < Latin ignōrant- (stem of ignōrāns), present participle of ignōrāre to ignore; see -ant

1. Ignorant, illiterate, unlettered, uneducated mean lacking in knowledge or in training. Ignorant may mean knowing little or nothing, or it may mean uninformed about a particular subject: An ignorant person can be dangerous. I confess I'm ignorant of mathematics. Illiterate originally meant lacking a knowledge of literature or similar learning, but is most often applied now to one unable to read or write: necessary training for illiterate soldiers. Unlettered emphasizes the idea of being without knowledge of literature: unlettered though highly trained in science. Uneducated refers especially to lack of schooling or to lack of access to a body of knowledge equivalent to that learned in schools: uneducated but highly intelligent.

Ignorant comes via Old French from Latin ignōrant-, the inflectional stem of ignōrāns, the present participle of ignōrāre “to be unaware of, be ignorant of, not know.” Ignōrāre also means “to disregard” and is the source of English ignore. Ignōrāre is related to the Latin verb gnoscere (more commonly noscere ) “to know,” from the same Proto-Indo-European root gnō- “to know” as English know and Slavic (Polish) znać “to know.”
An interesting use of ignorant appears in Mark Twain’s “Old Times on the Mississippi,” an essay he wrote for The Atlantic Monthly in 1875 and that was later incorporated into chapter 4 of Life on the Mississippi (1883): “This fellow had money, too, and hair oil. Also an ignorant silver watch and a showy brass watch chain.” By transferring the “lacking in knowledge” sense of ignorant from human beings to an object, the ever-clever Twain beautifully and succinctly described a timepiece that doesn’t tell the correct time.