Boomtang originates from music. It describes a piece of music or artist that is a cut above the rest, a genius. The music/artist can be depicted as having an extra panash, hence the 'tang'.
In later times the term is being used as general word to describe someting that is good e.g excellent, wicked ect.
that piece of music is boomtang!
Person 1: I got wasted last night and pulled a fit bird
Person 2: Boomtang!!!
imp is a minion of the underworld, a worthless servant, a bitch to do the cleaning.
Chimpy quite obviously orinates from the word chimpanzee. But chimpy describes a person that has chimp like features.
The two can be used together to descibe a devilish duo that although may seem retarded when seperate, together they are are deadly combination and can be percieved as being relatively normal.
Oy ya imp.
Hey he looks well Chimpy.
impy and chimpy have been up to there old tricks again.