Green’s Dictionary of Slang

sham abram v.

also sham abraham
[sham v.1 + abram n.]

1. [mid-18C–19C] (also play Abraham) to fake illness; also as n.

2. [late 18C–19C] of a beggar, to travel the country posing as a madman.

3. [1910s] (Aus.) to fake sanity.