Unknown. But it must be remembered that Grimmjow and all other Menos Grande are a fusion of many many Hollows and as such would not have had one single origin. Also, it has never been stated whether the personality that becomes dominant as a Menos or Arrancar is from one of the original Hollows or if it is a new personality created from their merger. Actually, it has been mentioned that if the original hollow has a greater ego or is stronger(i think), he keeps his personality.