FFXIV's DRK is a fusion of Rune Fencer and Dark Knight, just as Warrior is a fusion of Viking/Berserker/Warrior jobs. Rune Fencer specialized in great-swords and mitigating magic damage, which is a theme that DRK specialized in 3.0 (and less so in 4.0 due to the homogenization of tanks, but still there). Moreover, activating Blood Weapon creates red runes on your blade for a few moments during activation.

Also, Zidane used Dyne spells during trance, which awakens his true powers as a Genome from Terra. All his Dyne spells utilize Terran runes and script, and were abilities imbued in him at birth that he forgot about and only realized when he's under huge emotional stress.

That said, the swallow, or eku, is a weapon that originated from Okinawa and resemble and oar. They were only used for self defense but were basically double-sided naginata. I could see them being a weapon for a class that specializes in Staff/Pole in general. Kind of like Raijin in FF8 or any of the melee staves used in FFXI.