Due to your intimidating nature, people are inclined to give you the information you want to know. You are allowed in places that common folk would be barred from (such as prison cells or guard towers) in order to ask questions or interrogate others. When questioned, common folk are more likely to answer your questions and tell you the information you want to know, if they have it.
For as long as you can remember, you've found that you had a propensity for reading others. Understanding their motives, and wathcing their emotions change as you pull the truth out of them; you've always had a knack for getting just what you want out of people.
As you grew, you found that finding those that didn't want to be found came naturally to you. No matter where they hid, no matter who they paid to conceal them, you always found your mark. Your talents came in handy for finding those running from the consequences of their own actions.
When you choose this background, discuss the kinds of bounties you make have taken in the past with your DM. Did you only take ones officially issued by a governing force? Or did you offer your services to anyone who had the desire to find someone and a willingness to pay for your services? Would anyone you've had contact with hold a grudge? Are you hunting someone now?