If people do not know about what you offer then AdWords isn't the right way to attract visitors.
You need to have an established product or service that is already searched for to realistically make a return with ppc ads. Having said that, there are circumstances where you can piggy back on similar services or on searches that are not for your service but define the type of person who would want your offering.
If you have a product that's new and is used with an existing product to make it better then there's a chance you could promote the idea of your product to those searching for the existing product. "widget gloves" (let's say you normally can't use a widget with gloves on but you invent gloves that work) could be marketed in the winter on "widget" searches by promoting the benefit of keeping your hands warm whilst using the widget - people would be interested even though they didn't previously know about them as they are clearly widget users from the search they did.
If there's nothing close to do this with then you have a chicken and egg situation - you won't get an idea of the terms to use until you get traffic...