Stemming from the word 'Adjutant' which in the military is defined as 'an officer who acts as administrative assistant to a superior officer'. Adjutant is a position that generally gets fucked over and generally fucks others over. It is a thankless position.
When the abbreviation, 'adj', is used as a verb, it means to fuck over
; to treat unfairly; or to take advantage of. Sometimes used as to literally fuck.