It means complete and total frustration with a situation.
'I'm at my Wits End' comes from 'Keep your wits about you' meaning to keep focus, concentration and strength. Therefore to be at your wits end is to have run out of wits, running out of focus, attention, patience and strength.
You need the possessive apostrophe in the word wits' because you are at the end of your wits. I am at my wits' end to figure a way to make you do your work!
What does the word wits mean
The Cross-Wits ended in 1987.
It's not an idiom. Idioms make no sense unless you know the meaning already. "No end" means just what it looks like -- something is endless.
It's an idiom not a question.
"To be" is not an idiom - it's a verb.
Sorry, there is no such idiom as "at wit's put end to". "at wit's end" means you have tried every possible way to solve a problem but cannot do it and do not know what to do next. "put and end to" means to stop or put a stop to something.
Pest is not an idiom. It's a word.
The idiom "apple shiner" means the teacher's pet.
The meaning of the idiom in the pink of health means being in good health.
The Cross-Wits ended in 1987.