"Put money up" is a colloquial expression that means to contribute or invest money towards a particular project, purpose or purchase. It can also be used to refer to placing money as collateral or betting on an outcome. Some synonyms for "put money up" include investing, contributing, pledging, financing, funding, staking, wagering, backing, and putting down. These words may vary in meaning slightly but all involve the idea of putting forward financial resources. Each synonym can be used in different contexts and provide alternative ways to express the act of contributing money.