Meaning

noun an assumption that is taken for granted

noun (law) an inference of the truth of a fact from other facts proved or admitted or judicially noticed

noun audacious (even arrogant) behavior that you have no right to

originFrom pre- + Latin sūmptus + -ion, from Middle English presumpcioun, presumption, from Old French presumption and its etymon Latin praesūmptiō.

Etymology from Wiktionary, CC BY-SA 3.0