Green’s Dictionary of Slang

ackee n.

In phrases

in one’s ackee (also in one’s salt) [these positive emotions arise from being well-fed on ackee, a popular W.I. fruit of the Blighia sapida tree, usu. accompanied by saltfish]

(W.I.) energetic, cheerful.

[WI]cited in Cassidy & LePage Dict. Jam. Eng. (1980).