The expression 'to give someone a leg up' means to help someone improve their situation.
I have a great job in a posh restaurant. My mother gave me a leg up when she taught me to cook French dishes.
Mary had an uncle well connected to the business world. It gave her a leg up.
Don't confuse it with
The expression 'to pull someone's leg' means to play a trick on someone or tell them something that isn't true.
What?! You’ve won a million dollars in the lottery? You are pulling my leg.
According to some authors, cheerleading started around 1877 in the United States, when Princeton University students yelled chants from the stands at games. Nowadays most cheerleaders are women.