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

1) Not hard or difficult; requiring no great labor or effort.
2) Free from pain, discomfort, worry, or care (Dictionary.com).

M.E. aisie, esy, from O.Fr. aisie "comfortable, at ease, rich, well-off," p.p. of aisier "to put at ease," from aise "comfort, pleasure, well-being," of unknown origin.

Âsân "easy," from Mid.Pers. âsân "calm, quiet, at rest, peaceful, easy," related to âsudan "to rest, repose;" Av. ā- + saē- (saii-) "to lie down, go to sleep," → holiday.