Dolphin is reckoned the king of fishes, as the lion is of beasts, and many fabulous stories are told of him.
As that the dolphin is so much admired and beloved by other fishes, that they follow him about as their leader and chief; nay, they go so far as to affirm, that when he meets with a whale, he runs down into his belly, and turning round comes out again.
Others say, that the female dolphin has lugs, and gives suck to her young, to whom she is most loving;; that they have fallen in love with young men, have been very familiar with, and dy’d for grief of the loss of them.
That they out­swim all fishes, and when in pursuit of any one are drawn too near the shore, their motion is so rapid, that they often dash themselves in pieces against the rocks. That they observe great order, placing all the young ones in the van, next to them all their females, and in the rear, the males, that they may keep the others in view, and be always in a readiness to defend them.
These and many more conceits are written by grave authors, whence some will have the dolphin to be the emblem of a politick prince, who governs his people with prudence; and others make him the hieroglyphick of naval power.
But to pass all these conceits, the greatest honour done to the Dolphin, is being borne by the eldest son of the king of France; an there is good reason that that proceeded not from the excellency of the fish, but from the name only: For the Dauphins of Viennois, sovereigns of the province of Dauphine in France, the last of those princes having no issue, gave his dominions to the crown of France, upon condition tht the heir of the crown should be called Dauphine, and ever bear a dolphin for his arms, which they have accordingly done ever since, and so nice in preserving that bearing to themselves, as never to permit any other subject to bear it. But is is not so in England, the fish­mongers company bearing them in their coat, and several families have them in their arms.

Definition taken from The Universal Etymological English Dictionary, edited by Nathan Bailey (1736)

Diversiˊloquent * Doˊlphins [with Gunners]
Dioˊptricks, or Dio’pticks
Doˊlphins [with Gunners]
A white Dove
Doveˊs Foot
Doveˊs Tail Joint [in Joinery]
Dove Tailing [in Joinery]
Duˊnio [Old Writers]