Cldr.String.underscore

You're seeing just the function underscore, go back to Cldr.String module for more information.

underscore(atom)

This is the code of Macro.underscore with modifications:

The change is to cater for strings in the format:

This_That

which in Macro.underscore gets formatted as:

this__that (note the double underscore)

when we actually want:

that_that