in the NYC metro area in the early eighties among high school students it was very common to double up when affirming what state of being you were in.....used much like "hella" now, it was used in the positive when kids were "feeling good"....said in a kind of Dr. Seuss like cadence......stoners also adopted it in a slower cadence....started among students of European descent, but eventually spread to all groups....
Are you drunk?
I am I am!
response: You are you are!
Are you free last period? I am I am!
Stoner: Hey buddy, are you baked? I am I am.......he is he is