An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

1) A case or occurrence of anything.
2) An example put forth in proof or illustration (Dictionary.com).

M.E., from O.Fr. instance, from L. instantia "presence; earnestness, urgency," literally "a standing near," from instans, → instant.

Seté, from set, present stem of setâdan, variant of istâdan "to stand," → standard, + -é noun suffix.