Clown around town

bloodletting - shiv's 3, both have bleed over time skills (drifter 2)

cons: bit uncreative since it's literally his skill name

hot blooded: shiv's 4 Rage passive, blood for the vampires

cons: imo not terribly obvious it's for drifter and shiv, even if you know it's meant to be a ship name

stab in the dark: shiv's blades and knives, drifter's 4

cons: phrase itself (to blindly guess) doesnt really have much to do with their of them, not a compound word and is bit longer of a ship name

other

baboon's blood: scottish play reference after drifter's kill quote for shiv "feels shakespearean dont it shiv?", one of the ingredients for the witches' potion, dunno why but the monkey vibes shiv got also works