lesson (n.) Look up lesson at Dictionary.com
early 13c., "a reading aloud from the Bible," also "something to be learned by a student," from Old French leçon, from Latin lectionem (nominative lectio) "a reading," noun of action from past participle stem of legere "to read" (see lecture (n.)). Transferred sense of "an occurrence from which something can be learned" is from 1580s.