/usr/bin/Fenv is in ferret-vis 6.6.2-3.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 | #! /bin/csh -f
# Fenv
# list the environment variables relevant to the FERRET program
ferret_paths
env | grep FER
|