The meaning and origin of the expression: The Devil incarnate

The Devil incarnate

What's the origin of the phrase 'The Devil incarnate'?

In 16th century England the devil was considered to be a real living entity that roamed the land and was able to transform itself, or at least inhabit, other living beings. The expression 'the devil in human form' wasn't a metaphor as we might use it now but an actuality. The first reference to it that I know of in print is in the collection of tragic poems The Mirour for Magistrates, 1578:

A wicked wretch, a kinseman most vnkynde [unkind],
A Deuil incarnate, all deuilishly enclynde [inclined]

The expression must have been in common usage in the late 16th century as Shakespeare also used it, without any explanation, in King Henry V, 1598, and Titus Andronicus, 1588:

Henry V - Boy: Yes, that a' did; and said they were devils
incarnate.

Titus Andronicus - LUCIUS: O worthy Goth, this is the incarnate devil
That robb'd Andronicus of his good hand.