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