It sounds French, so I like it already. The word “enallage” is derived from the Greek word ἐναλλαγή, meaning “interchange.”
By definition, it is a term used to mean the substitution of one word with another one with the same or similar meaning, but with a different (possibly incorrect) grammatical form. Here’s an example: Professional prize-fight manager Joe Jacobs’ 1932 cry of We was robbed! after his fighter lost a decision.
Enallage may be used to connect more closely with the listener, or reader. Look at you! She who is beautiful.
Sometimes enallage is deliberate in your character’s speaking style. If your character is not a native English speaker, you might use enallage to demonstrate that. Just make sure you use this device sensibly.
And my favorite opening line is a great example of enallage: “You better not never tell nobody but God.” Who can name the book?