bender (n.)

late 15c., "instrument for bending," agent noun from bend (v.). Slang meaning "drinking bout" is American English, attested from 1846, perhaps from the Scottish sense of "a hard drinker" (1728). Perhaps from the verb in the figurative sense of "strain, brace, wind up." Other slang senses included "a sixpence" (1836) "( ? Because it bends easily.)" [OED]; "a leg" (U.S., 1849).