Euclid has just defined points, and stated that the extremities of lines are points; ... Then the use of the same symbol for different points (AA, BB, ΓΓ denoting segments) ...

Oliver Byrne. The First Six Books of the Elements of Euclid, in which Coloured Diagrams and Symbols are Used instead of Letters for the Greater Ease of Learners (London: Printed by Charles Whittingham ...