In Europe, it is in many countries the short form of fashist.
In Germany, for instance, "ein Fascho" translates to "a fashist", or "das ist aber fascho" (eng. "that is so fashist"). Even
Google Translator translated "Er ist ein Fascho" into "He is a fascist", and
equivalent to "fascho" (adjective).
It is, however, not related to the American Black slang of "fasho" as "for sure".