|pre-1967 plus paint|
A posting on Newton, IL refers to this east/west route as "The High-Dry" line. So evidently the north/south IC/PD&E route through Newton was effectively the Low-Wet route because of its vicinity to the Embarras River.
Update: this route has the famous Tulip Trestle and the Shuttle Creek Trestle. According to a comment by Richard Koenig in a Bridge Hunter post, this route was nicknamed the Hi-Dry. He also explains that since IC is a north/south railroad, they retain that convention on this east/west branch with Indianapolis being at the north end.
The eastern part of this route is now operated by the Indiana Rail Road.