In Elizabethan slang, it means 'wooden head' or 'block head'. It comes from 'clodpoll'.
The word 'clatpole' is used in Shakespeare's Troilus and Cressida, Act 2, scene 1, lines 110–120.
Ajax:
I shall cut out your tongue.
Thersites:
'Tis no matter, I shall speak as much as thou afterwards.
Patroclus:
No more words, Thersites, peace!
Thersites:
I will hold my peace when Achilles' brach bids me, shall I?
Achilles:
There's for you, Patroclus.
Thersites:
I willsee you hang'd like clatpoles (clotpole) ere I come any more to
your tents. I will keep where there is wit stirring, and leave the
faction of fools. *Exit*
who are you even, some new fucking cookie who thinks they’re big game? Sorry but the world doesn’t work that way neither does it revolve around you. You were basically irrelevant and unexistent until now. I changed that. You are now another one of “Cyber’s” Sworn rivals, you could consider yourself famous around hhere cuz of that now. you should thank me. Because i made you relevant. So don’t fucking try me, because i can make u just as easily irrelevant again. Fucking clotpole.