Green’s Dictionary of Slang

abraham’s balsam n.

[SE Abraham’s balm, the chaste tree (Vitex agnus-castus), but presumably punning on Abraham’s bosom, the abode of the dead (see next)]

the gallows.

[UK]Farmer & Henley Sl. and Its Analogues I 10/1: abraham’s balsam (old.) – Death by hanging.