Unless you hide it under your mattress, you probably keep your money in a bank, or a business that stores and invests money.
There are several different meanings of the word bank. Besides the ones connected with money — like a savings bank or a piggy bank — a bank is also a slope of grass or earth, such as a river bank. Both of these are rooted in a Germanic word, bankiz, or "bank of earth." From this root came words meaning "shelf" and "table." The money-related bank came from the "table" meaning, banque in Middle French, as in "moneylender's exchange table."