In Greek mythology, Hippocrene (Ἱπποκρήνη) was the name of a fountain on Mt. Helicon. It was sacred to the Muses and was formed by the hooves of Pegasus. Its name literally translates to 'Horse's Fountain' and the water was supposed to bring forth poetic inspiration when imbibed.
Keats refers to Hippocrene in his poem Ode to a Nightingale.
O for a beaker full of the warm South
Full of the true, the blushful Hippocrene,
With beaded bubbles winking at the brim,
And purple-stained mouth;
That I might drink, and leave the world unseen,
And with thee fade away into the forest dim:
Hippocrene Books is named for the Hippocrene fountain.