What is the word, imprimis? (From Shakespeare's The Taming of the Shrew)

Imprimis means in the first place.

GRUMIO: . . . Now I begin: / Imprimis, we came down a foul hill, my master riding behind my mistress, --
CURTIS: Both of one horse?
GRUMIO: What's that to thee?
CURTIS: Why, a horse.
From Shakespeare's The Taming of the Shrew, Act IV, Scene 1.