bender

Hypotheses:

bend +‎ -er. In sense of “heavy drinking”, originally generally “spree”, from 1846, of uncertain origin – vague contemporary sense of “something extraordinary”, connection to bend (e.g., bending elbow to drink (bend one's elbow)) or perhaps from Scottish sense of “strong drinker”.

In Britain, for about four centuries, a sixpence was known as a bender because its silver content made it easy to bend in the hands. This was commonly done to create ‘love tokens’, many of which survive in collections to this day. The value of a sixpence was also enough to get thoroughly inebriated as taverns would often allow you to drink all day for two pence. This gave rise to the expression ‘going on a bender’.

(interjection): From over the bender, referring to a person's arm (and sometimes accompanied by a gesture of the thumb backward over the shoulder); compare over the left shoulder.