E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
per se [I by itself], i.e. without compeer, pre-eminently so.
If then your I [yes] agreement want,
I to your I [yes] must answer, No.
Therefore leave off your spelling plea,
And let your I [yes] be I per se.
i.e. let your yes be yes decidedly.
Wits Interpreter, p. 116.
Many other letters are similarly used; as, A per se. (See A-PER-SE.) Thus in Restituta Eliza is called The E per se of all that ere hath been. So again, O, signifies a crier, from O yes! O yes! We have Villanies descovered by the help of a new crier, called O per se [i.e. superior to his predecessors]. 1666.
Shakespeare, in Troilus and Cressida, i. 2, even uses the phrase a very man per se = A 1.