Origins
The word 'lecture' entered English around 1350 from Medieval Latin 'lectūra,' meaning 'a reading,' derived from 'lectus,' the past participle of Latin 'legere' (to read, to gather, to choose). The word shares its root with 'lesson' (from Latin 'lectiō,' also 'a reading'), and the two words traveled parallel paths from the same source into English, diverging in register: 'lesson' settled at the school level, 'lecture' at the university level.
The connection between 'lecture' and 'reading' is not merely etymological but historically literal. In the medieval European university — from Bologna and Paris in the twelfth century onward — the primary method of instruction was the 'lectio,' a formal reading aloud. A master would sit at a raised desk and read from an authoritative text — Aristotle's Physics, Justinian's Digest, Peter Lombard's Sentences — while students listened and took notes. Books were handwritten, enormously expensive, and often the professor possessed the only copy in the room. The 'lectūra' was the act of reading that text to an audience; the 'lector' (reader) was the person who performed it. The word 'lecture' thus names a specific technological constraint: in a world before printing, knowledge was transmitted by one person reading to many.
The PIE root *leǵ- (to gather, to collect) produced Latin 'legere,' one of the most prolific source verbs in the English lexicon. Its original meaning was 'to gather' — to pick up items one by one. This concrete sense of gathering evolved into 'to gather letters with the eyes,' hence 'to read.' The semantic shift from physical gathering to reading is not unique to Latin; English 'to read' itself originally meant 'to advise, to interpret' (as in German 'raten,' to advise), and 'to gather' the meaning of a text is a metaphor English still uses.
Proto-Indo-European Roots
From 'legere' and its compounds, English inherited a vast word family. 'Lesson' (a reading), 'legend' (a thing to be read — originally the story of a saint's life read aloud on their feast day), 'legible' (capable of being read), 'lection' (a reading from scripture), and 'lector' (one who reads aloud) all derive from the base verb. The compound forms are equally productive: 'collect' (con- + legere, to gather together), 'elect' (ex- + legere, to choose out), 'select' (se- + legere, to choose apart), 'neglect' (nec- + legere, not to pick up), 'intellect' (inter- + legere, to choose between, hence to understand), and 'diligent' (dis- + legere, to single out, hence to be careful). Through Greek 'légein' (to say, originally to gather), the same PIE root produced 'logic,' 'logos,' '-logy,' 'analogy,' and 'dialogue.'
The shift of 'lecture' from 'reading' to 'oral presentation' tracks the transformation of university teaching. After Gutenberg's printing press (c. 1440) made books widely available, the rationale for reading aloud from a single manuscript disappeared. Professors were free to speak in their own voices, to develop original arguments, to respond to questions. The 'lecture' evolved from recitation to discourse — but the word remained, a fossil of the manuscript age embedded in the language of modern education.
The secondary meaning of 'lecture' — a tedious or reproving speech — appeared in the seventeenth century, reflecting the common complaint that academic lectures were boring. 'Don't lecture me' transfers the classroom dynamic to personal relationships: the speaker objects to being treated as a passive audience for someone else's monologue. This pejorative sense has no parallel in French, where 'lecture' still simply means 'reading' (the act of reading a book), and a university talk is called a 'cours.' The English sense of 'lecture' as oral discourse — whether academic or admonishing — is a semantic development unique to English among the Romance-influenced languages.