What do you call it when you transpose the last two words of a sentence on purpose? [duplicate]

What do you call it when you transpose the last two words of a sentence on purpose?

Such as: "Once upon a midnight dreary" Instead of "Once upon a dreary midnight?"

Or: "Hark! What light through yon window breaks" Instead of "What light is breaking through that window?"

Or: "God rest ye merry gentleman, let nothing you dismay?" Instead of "...Let nothing dismay you?"

As per tchrist's answer to the linked possible duplicate, a technical term for this is anastrophe:

Inversion of the normal syntactic order of words; for example, "Matter too soft a lasting mark to bear" (Alexander Pope). - thefreedictionary.com

A more general term, but one that is in more widely used and that best covers the motive for doing such a thing would be poetic licence:

The liberty taken by an artist or a writer in deviating from conventional form or fact to achieve a desired effect. - thefreedictionary.com