US-ASCII en · PROPN
Etymology
From US (“United States”) + ASCII.
Meanings
-
(formal, retronym) Synonym of ASCII, especially to differentiate it from 8-bit extended ASCII.
Here, we see that the source encoding has fallen back to US-ASCII because none was explicitly set.
2009, Gregory T. Brown, Ruby Best Practices, O'Reilly, →ISBN, page 189: