Merriment is a related term of joyfulness.
As nouns the difference between merriment and joyfulness
is that merriment is a state of enjoyable exuberance while joyfulness is the state of being joyful.
merriment
English
Noun
a state of enjoyable exuberance
*
playful fun
*
joyfulness
English
Noun
(-)
the state of being joyful