from The Century Dictionary and Cyclopedia
- n. The carp, Cyprinus carpio: so called from its supposed cunning. 1 Walton. Compare water-sheep.
Sorry, no etymologies found.
And you may take notice, that as the Carp is accounted the water-fox, for his cunning; so the Roach is accounted the water-sheep, for his simplicity or foolishness.