(Note: for the definition E-NED has 'see quot.';
The quotation shows 'fat person' - see below;
however, in the online book I found, as shown below in the Example (1777),
it is 'fat parson' not 'fat person'
from jolly (adj.):
cf. dialect. jollus and jollous jolly-looking, fat, fleshy
a 1797 - An Ode to Sir Fletcher Norton, William Mason;
see Example below
From: An Epistle to Dr. Shebbeare:
To which is added an Ode to Sir Fletcher in Imitation of Horace
By William Mason
Third Edition 1777
Ode to Sir Fletcher Norton in Imitation of Horace
Ode VIII. Book IV.