good for

Beneficial to, as in Milk is good for children . [Tenth century a.d. ]

Financially reliable, able to pay or repay, as in They know he's good for a big tip . [Mid-1800s]

Able to serve or continue to function, as in This furniture's good for at least ten more years , or I hope you're not tired—I'm good for another three miles or so . [Mid-1800s]

Equivalent in value; also, valid for. For example, These coupons are good for a 20 percent discount , or This contract is good for the entire life of the book . [Second half of 1800s]

good for someone . An expression of approval, as in Good for Bill—he's sold the car , or Good for you! You passed the exam . This usage differs from the others in that orally a slight emphasis is placed on you or whoever is being mentioned. [Mid-1800s]