G'day Dicho,

"... always thought kicked the bucket was American (Mencken, "The American Language," says it is, and western ..."

It's difficult to tie this sort of thing down, since the really 'authoritative' texts only consider published usages. Slang can slip through the net - until someone uses it in a book or journal. A few good examples show up in The 1811 Dictionary of the Vulgar Tongue (a reworking of Capt. Grose's 1797 Dictionary of London Street Slang and University Wit). This contains terms like:

Screw = Sexual intercourse
and
Pig = Policeman (or equivalent of the day)

These (and similar) words had completely fallen out of London use by mid-nineteenth century ... but re-appeared in 20th century American novels - and were thus considered to be "American neologisms" - until arcane little dictionaries like this one began to be dragged out of collections and republished in facsimile.

Regards,

Bob Bolton (the one whose dictionary bookcase needs expansion ... again!)