The Collaborative International Dictionary of English v.0.48:
Haddock \Had"dock\ (-d[u^]k), n. [OE. hadok, haddok, of unknown
origin; cf. Ir. codog, Gael. adag, F. hadot.] (Zool.)
A marine food fish (Melanogrammus [ae]glefinus), allied to
the cod, inhabiting the northern coasts of Europe and
America. It has a dark lateral line and a black spot on each
side of the body, just back of the gills. Galled also
haddie, and dickie.
Norway haddock, a marine edible fish (Sebastes marinus)
of Northern Europe and America. See Rose fish.