What is "herring hag"

Porpoise \Por"poise\, n. [OE. porpeys, OF. porpeis, literally, hog fish, from L. porcus swine + piscis fish. See Pork, and Fish.]

1. (Zo["o]l.) Any small cetacean of the genus Phoc[ae]na, especially Phoc[ae]na communis, or Phoc[ae]na phoc[ae]na, of Europe, and the closely allied American species ( Phoc[ae]na Americana). The color is dusky or blackish above, paler beneath. They are closely allied to the dolphins, but have a shorter snout. Called also harbor porpoise, herring hag, puffing pig, and snuffer.

2. (Zo["o]l.) A true dolphin ( Delphinus); -- often so called by sailors.

   Skunk porpoise, or Bay porpoise (Zo["o]l.), a North American porpoise ( Lagenorhynchus acutus), larger than the common species, and with broad stripes of white and yellow on the sides. See Illustration in Appendix.