Behind your back
When something happens behind your back it happens without your knowledge or when you were absent.
As the decision to divide the property was taken behind my back I didn’t know anything about it until it was too late.
To have butterflies in your stomach
To have butterflies in your stomach is to have a feeling of fear or anxiety.
It was her first stage performance and she had butterflies in her stomach.
A shot in the arm = something which has a positive effect on somebody or something else
The opening of the new laboratory will give a much-needed shot in the arm for cancer research in India.
The long arm of the law = the judicial system in the country
I told him that he must not do it. No one can escape the long arm of the law.
To cost an arm and a leg = When something costs an arm and a leg, it is extremely expensive.
A good laptop still costs an arm and a leg.
Strong-arm = to use strong-arm tactics is to use force and threats to make people obey
The police used strong-arm tactics to disperse the violent mob.
To twist someone’s arm = to pressure someone to do something they don’t want to do
I had to twist his arm a little, but he agreed.
Back to back = consecutively and without interruption
She presented three speeches back to back.
Behind someone’s back = to do something without them knowing
I signed the contract behind his back and now he is really angry with me.