after the standard pattern (payee = one that is paid), staff member = person who is required, devotee = one that is committed), an attendee must be somebody who is attended, in other words., the SPEAKER not the ATTENDERS into the audience.Used (with other similar patterns) by individuals too lazy to look within the proper word.
"one whom attends" (some thing), 1961, from attend + -ee. Attender is older (mid-15c.) but had sensory faculties "one whom waits upon" and "one whom offers heed."
an individual who occurs and participates in a meeting