Alexander Dyce, A General Glossary to Shakespeare's Works

sessa THE TAMING OF THE SHREW, Induction, 1. 5; KING LEAR, iii. 4. 99; iii. 6. 73. This, according to Theobald, is the Spanish “Cessa, that is, be quiet;” according to Hanmer, “Peace, be quiet, Lat. Cessa;” according to Capell, a “corruption of cessa (Ital.) and cessez (Fr.), both deriv'd from the Latin word cessa, and both signifying, as that does, ‘leave, have done, let alone;’” and Johnson (with whom Nares in Gloss. agrees)“takes it to be the French word cessez . . . an interjection enforcing cessation in any action, like be quiet, have done.” (I must confess that I do not feel satisfied with these notes on sessa: qy. if the word, as used in at least the second and third of the passages above referred to, may be illustrated by the following lines of Sylvester's Du Bartas, ed. 1641? Joshua urges on his troops:
“Sa, sa, my Hearts! turn, turn again upon them,
They are your own; now charge, and cheerly on them.”
The Captaines, p. 182; where the original has “Cà, cà, tournons visage, allons,” etc.; Jezebel being killed,
“The Dogs about doe greedy feed upon
The rich-perfumed, royall Carrion;
And Folk by thousands issuing at the Gate
To see the sight, cry thus [as glad thereat]
Ses, ses, here Dogs, here Bitches! doe not spare
This Bitch that gnaw'd her subjects' bones so bare.”
The Decay, p. 229; where the original has “Sus, lyces, deschirez,” etc.) Compare, too: “Spa. Well played, dog! well played, bear! Sa, sa, sa! to 't, to 't!” Ford's Fancies Chaste and Noble, act iv. sc. 1.