Odin is using his wit to win over Mimer. He wanted to be the wisest man in the world. He has a strong desire to have a draught from Mimer's precious spring and to be able to get what he wanted he has bargained his eye for it( that is how Odin lost his one eye). In order to become the only wisest man in the world, he deceived Vanir by sending his foolish brother. When giant Mimer thought that Hoenir that he must be equally wise like his brother Odin, he made him as the chief of Vanir.
Whenever Mimer was absent he would
look nervous and frightened, and if folk questioned him he always answered:
"Yes, ah yes! Now go and consult someone else! which made the people mad. They thought Mimer has deceived them, so they cut off Odin's head and give it to Odin as a present. Odin got what he wanted--to be the wisest of all men in the whole world.