"in the rear, in a backward state," especially "insolvent, unable to pay," 1520s, from prepositional phrase; see behind, probably on model of beforehand (q.v.).
a company that has been run behindhand for years
was behindhand with the rent
behead
beheld
behemoth
behest
behind
behindhand
behold
beholden
beholder
behoof
behoove