While by all apearances the term "dirk" seems to have originated in Scotland, it was quickly adopted as a name for any number of weapons, typified as a single-edged, drop-pointed knife suitable for thrusting.
It is the "stabbing" part that gets the lawmakers, who couldn`t find their asses in the dark if they used both hands, to classify a double-edged, or in deed anything capable of stabbing or piercing, as a dirk.
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"One of God`s Prototypes. A powerful mutant, never even considered for mass-production.
Too weird to live. Too tough to die."