[Scarlett.]

Wildcat, you fail

Swagger dates all the way back to Shakespeare's "A Midsummer Nights Dream"

'PUCK

What hempen homespuns have we swaggering here,
So near the cradle of the fairy queen?
What, a play toward! I'll be an auditor;
An actor too perhaps, if I see cause.

QUINCE

Speak, Pyramus.—Thisby, stand forth.

PYRAMUS

'Thisby, the flowers of odious savours sweet,'

QUINCE

Odours, odours. "

Wikisource

Etymology

Frequentative form of swag (“‘to sway’”); attested 1590, A Midsummer Night's Dream III.i.79:

You just got "schooled" biatch