When you `curry favor with someone' you try to gain a person's approval by making use of flattery. You attempt to win the individual's support by talking to him rather politely, very often resorting to insincere praise. The expression is normally used to show disapproval.

Prakash is trying to curry favor with his uncle again.

The `curry' in the expression has nothing to do with the curry we eat. This curry comes from the world of horse riding. People who take care of horses make use of a `curry- comb' to rub the animal down. It is from this, that we get the expression `to curry', meaning `to groom a horse'. In other words, the verb `to curry' means to rub down a horse. The word `favor' in the idiom has got nothing to do with the favor we know. It is, in fact, a corruption of the French name `Favel' (also spelt `Favel'). Favel is the name of a cunning centaur that appears in a French story written in the 14th century. A `centaur', as you probably know, is an animal that is half man and half horse. In the story, people who wanted to be on the good side of the evil Favel, used to flatter him and also rub him down. In other words, the characters in the story used to `curry Favel'. In fact, the original expression was `to curry Favel'. Since `Favel' sounded like `favor', native speakers of English started saying, `to curry favor'.