Yours, Etc.: Origins and Uses of 8 Sign-Offs
something steeped in pickle, especially "pig parts preserved and pickled," mid-15c., earlier "liquid for pickling" (late 14c.), from souse (v.) or from its French source.
[fr an extension of souse, ''pickle brine, something pickled,'' hence semantically akin to soak, ''drunkard,'' and pickled, ''drunk'']