ETYMOLOGY
the first element, tara, is of obscure origin;
+ diddle (n. a swindle, deception) (vb. to cheat, to swindle)
EXAMPLE
“…Bar. My dear Anna Matilda, I don’t know myself; so how can I tell you?
Mrs. B. There’s a bare-faced tarradiddle, Mr. Barbottle…”
From: The Duel:
Or, My Two Nephews
A Farce, in Two Acts
By R. B. Peake, 1823
Lexicophilia 