If you
go hat in hand to someone, you ask them very humbly and respectfully for money or help.
The state had to go hat in hand to financiers in New York, London, and Boston to rescue its finances. He won't go hat-in-hand to the White House to ask that sanctions be lifted against his country. Note: The usual British expression is
go cap in hand to someone. Note: In the past, it was customary for lower-class people to remove their hats in front of upper-class people. The expression may also refer to the fact that people sometimes hold out their hats when they are begging, for other people to put money in.