Filmishmish (في المشمش) is an Arabic term meaning "in the time of the apricots" or "when the apricots bloom", which is taken nonliterally to mean the equivalent of the English phrases "wishful thinking" or "when pigs fly." It is also the final lyric of the song "When the President Talks to God" by artist Bright Eyes.
References
Filmishmish Wikipedia(Text) CC BY-SA