'eighteenth of June' appears in the poem, "Napoleon's Farewell to Paris," no relation to the song, but mentioning the same event. One of the ten verses:

My golden eagles were pulled down by Wellington's allied army
My troops, all in disorder, could no longer stand the field;
I was sold that afternoon, on the eighteenth of June,
My reinforcements proved traitors, which caused me to yield.

On a sheet with "The Nut Girl," printed by Taylor, Spitalfields, London, no date. American Memory.