commander of the Fleet, n. — Green’s Dictionary of Slang

commander of the Fleet n.

[pun on fleet/Fleet; the prison name refers to the Fleet River, itself f. OE fléot, a tidal inlet]

the warden of the Fleet prison.

1811

Lex. Balatronicum n.p.: Navy Office. The Fleet prison. Commander of the Fleet; the warden of the Fleet prison.