related -- I found the usage example of say't

From Shakespeare "Winter's Tale"

Ha' not you seen, Camillo,--
But that's past doubt, you have, or your eye-glass
Is thicker than a cuckold's horn,--or heard,--
For to a vision so apparent rumour
Cannot be mute,--or thought,--for cogitation
Resides not in that man that does not think,--
My wife is slippery? If thou wilt confess,
Or else be impudently negative,
To have nor eyes nor ears nor thought, then say
My wife's a hobby-horse, deserves a name
As rank as any flax-wench that puts to
Before her troth-plight: say't and justify't.