Brewer's: Jolly Good Fellow
(A). A very social and popular person. (French, joli.)
“Ali was jolly quiet at Ephesus before St. Paul came thither.” —
For he's a jolly good fellow [three times]. And so say all of us, With a hip, hip, hip, hoora!
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894