late 14c., "action of reading, that which is read," from Medieval Latin lectura "a reading, lecture," from Latin lectus, past participle of legere "to read," originally "to gather, collect, pick out, choose" (cf. election), from PIE *leg- "to pick together, gather, collect" (cf. Greek legein "to say, tell, speak, declare," originally, in Homer, "to pick out, select, collect, enumerate;" lexis "speech, diction;" logos "word, speech, thought, account;" Latin lignum "wood, firewood," literally "that which is gathered").
To read is to "pick out words." Meaning "action of reading (a lesson) aloud" is from 1520s. That of "a discourse on a given subject before an audience for purposes of instruction" is from 1530s.
1580s, from lecture (n.). Meaning "to address severely and at length" is from 1706. Related: Lectured; lecturing.