The origin of the current use of trunk (or TRUNK or TRUNK TRUNK or any other derivative) comes from this message from bigD:

"We stopped about 95 miles south of jaspa to gas up yesterday and to
let ASD walk around a bit. He was getting kind of cranky by thte
time we got to jasper so we stopped at a park to let him play for a
while. He got out and started walking to the park and his assend was
all wet. Wif checked him ote and he had bigtim shit himself. It
soaked through his diaper and pants and carseat. yuck. we changed
him on the trunk trunk of the car.

in summary I can't believe that

A) he shit himself that bad in 90 minutes
and
A) he wasn't complaining more about it

naxt"

TP caught the typo and LOLed about it and teh rest is history!

Usage Examples:
"TRUNK TRUNK!"
"What the trunk?"
"What you gon' do with all that trunk?
All that trunk inside your trunk?
I'ma get, get, get, get, you drunk
Get you trunk drunk off my trunk
My trunk, my trunk, my trunk, my trunk, my trunk, my trunk
My trunk, my trunk, my trunk, my lovely little trunks. (trunk it out)"