Green’s Dictionary of Slang

abraham-man n.

also abraham-cove
[? the Abraham Ward of the Hospital of St Mary of Bethlehem, London, in which the insane patients were housed. The hospital, known popularly as Bedlam, allowed certain inmates to go begging on a number of fixed days each year; the abram-man posed as one of these licensed beggars. Note the parable of the beggar in Luke 16:19–31; Ribton-Turner, A History of Vagrants (1887), suggests Gaelic/Erse bramanach, a noisy fellow; + SE man/cove n. (1)]

[mid-16C–mid-19C; 1930s] a wandering beggar, adopting tattered clothing and posing as a madman.