early 15c., "official examination of accounts," from Latin auditus "a hearing, a listening," past participle of audire "to hear" (from PIE root *au- "to perceive"). Official examination of accounts originally was an oral procedure. Also formerly used in a sense "official audience, judicial hearing or examination" (1590s).
mid-15c., "examine and verify (accounts)," from audit (n.). Meaning "attend (a course, etc.) without intending to earn credit by doing course-work" is from 1933. Related: Audited; auditing.