1878, Amer.Eng. and Canadian Eng., of unknown origin, perhaps from Mex.Sp. jacal, from Nahuatl xacalli "wooden hut." Or perhaps a back-formation from dial. Eng. shackly "shaky, rickety" (1843), a derivative of shack, a dial. variant of shake (q.v.). Another theory derives
shack from ramshackle. Slang verb phrase shack up "cohabit" first recorded 1935 (in Zora Neale Hurston).