"Persona" (personae) as used by Pound, by most or all critics, is from
the Latin, and it means "mask" (the kindof masks worn by actors on the
Roman stage. It was imported into 20-th century literary criticism as a
convenient term to distinguish the speaker of a poem from the poet.
When Pound gave his early Collecte Peoms the title of Personae he was
indicating that he assumed a wide number of differnt "masks," playing,
as it were, many parts. Swift's _persona_ in A Modest Proposal is that
of a Projector as that term was used in the early 18th-c, A Man With A
Plan as it were. The Puritan Marvell takes the Mask/Persona of a seducer
to write To His Coy Mistress. Dramatic monologues, as in Browning, are a
different matter. It is not Browning donning a mask to speak but
Browning creating a dramatic character. Debates over "Prufrock" in the
poem seem to be, in part, debates over whether Eliot has created a
Browningesque dramatic monologue or whether Prufrock is a Persona
through which Eliot speaks.
Ooops! I almost forgot the most important feature of a _persona_; it was
constructed so as to magnify the actor's voice. If you read through
mid-10th century criticism you will constantly run into the word
_persona_ used in this sense.