Green’s Dictionary of Slang

sham-Abraham adj.

fraudulent.

1828		‘A Flat Enlightened’ Life in the West II 35: His [...] plight deceived all the spectators bar those previously acquainted with how the result was to be, who knew that the principal part was all ‘sham Abraham’.
1838		Paul Pry 30 Sept. 181/2: Why [...] he should have been such an ass in his old age as to let his spe culations [...] be carried so far as to cause the shutting up of his sham-Abraham-bank.