ETYMOLOGY
irregular from jolly (adj.) + -ment
EXAMPLE
“… And therein sate a Ladie fresh and faire,
Making sweet solace to her selfe alone;
Sometimes she sung, as loud as larke in aire,
Sometimes she laught, that nigh her breth was gone,
Yet was there not with her else any one,
That might to her moue cause of meriment:
Matter of merth enough, though there were none
She could deuise, and thousand waies inuent,
To feede her foolish humour, and vaine iolliment. …”
From: The Faerie Queene
By Edmund Spenser, 1590
Lexicophilia 