The unit name are stored in a YAML file located in avalon/config/controlled_vocabulary.yml.  The controlled vocabulary file has key value pairs that store.  This file is loaded every time it is needed and is never cached.  Therefore, the file can be changed without restarting Avalon.

# Each list member is prefixed with a hyphen and indented with two spaces.
# The Avalon codebase uses two spaces for indentation.
  - University Archives
  - Art Collection

Changing and Removing Unit Names

The purpose of the unit vocabulary is to ensure that collections are saved with a proper unit.  Changing or removing unit names in the controlled vocabulary file will not update or remove those unit names from collections.