From Middle EnglishJake(variant of “Jack”) or Jakke(variant of “Jacques” and “Jack”). Use as a place to urinate and defecate first attested in the form jacques.[1] Compare terms such as US slang Cousin John and Quincy, used as euphemistic personifications the speaker was "visiting".
[…] Whereas the Truth-finder, having raked out that Jakes his own Mind, and being there capable of tracing no Ray of Divinity, nor any thing virtuous, or good, or lovely, or loving, very fairly, honestly, and logically concludes, that no such things exist in the whole Creation.
And the treasures of the floor and walls went raw into the jakeses from my brush and dustpan: sludges, geodes, hair, dead insects and arachnidae, a rubber glove and tainted paper waste, a mouse's skull and tail, a set of used plasters, […]