Have a corncob up (one's) ass American vulgar slang
Used to describe someone who is extremely rigid or inflexible in their posture or demeanor
She was so nervous that she had a corncob up her ass.
I know he has a real corncob up his ass from the way he speaks.
Used to describe someone who is extremely rigid or inflexible in their opinions or beliefs
She has a real corncob up her ass when it comes to her emotional and sexual life.
Used to describe someone who is irritable, unfriendly, or humorless
James must have had a corncob up your ass or something when his friend played a trick on him.
The verb "have" should be conjugated according to its tense.
To decide to believe someone‘s saying although they may not tell the truth
He said that he was late because he had an accident and I gave him the benefit of the doubt.