Something that is prevalent or most common can be described as prevailing. The prevailing opinion in your family might be that your cousin Bob who sleeps in his closet is certifiably insane.
The adjective prevailing comes from the Latin words prae, meaning before, and valere, meaning to be strong or have power. The English word maintains that sense of strength and predominance. If you live a couple of miles north of a pig farm, and the weatherman says that the prevailing winds will be from the south and gusty, it's probably a good day to keep your windows closed.