means The trade in something illegal or exploited — most damningly the buying, selling, and forced movement of human beings for labor or sex.

from From "traffic," which entered English in the early 1500s from French "trafique" and Italian "traffico," meaning commerce, trade, the movement of goods. Its deeper roots are murky — possibly the verb "trafficare," to trade or peddle, though no one is certain how that word itself was built. For centuries "traffic" simply meant the flow of business and, later, the flow of vehicles. The grim "-ing" sense — dealing in things that ought never be dealt in, like drugs, weapons, and people — grew from the older idea that traffic is anything moved and sold, no matter how monstrous the cargo.