from The Century Dictionary and Cyclopedia
- In Roman antiquity, a joyous festival in honor of Cybele, celebrated at the vernal equinox.
Sorry, no etymologies found.
As a result, the word hilaria from the Latin hilaris which means cheerful. and the Greek hilaros which means glad came to refer to any festival of rejoicing.
* All the ancient festivals respecting the return and exaltation of the sun were of this description: hence the hilaria of the Roman calendar at the period of the passage,