The family crest, infact even the origins of the Killen family are difficult. Through my research i have discovered that if you originate from the west of Ireland, you belong to the O'Cillin (Killeen) clan. The Killeen's dropped an 'e' when they emigrated mostly to the America's so they didn't sound so Irish, as at the time the irish were being persecuted somewhat. If your family originated from Ulster in the north, then you belong to the McQuillan (McKillen)clan. It has been a long difficult exhausting road finding all this out. Hope this has helped everyone with the surname Killen.