Is a contraction of the words pill and Chillicothe. Chillicothe is a small city that sits in the scioto valley in south-central Ohio. The highway that goes thru the city is a well known drug trafficking route, linking Columbus and parts of Kentucky. The rapid increased abuse of pills in the region, starting in the late 1990's, is what led to the nickname.
"Another kid overdosed this week. I guess that's Pillicothe for ya."