Why are subtropical high pressure zones called "the trade winds"?

The term "trade winds" refers to the regular winds that blow from the subtropical high pressure zones toward the equator in roughly westerly directions. They are so named on account of the way trading ships used these winds when sailing west from Europe to the Americas.

Occupying the regions from roughly 5 degrees to 30 degrees latitude on both the north and south sides of the equator, the trade winds are quite steady with an average speed of roughly 11 to 13 miles per hour. In the Northern Hemisphere, these winds blow from the northeast. In the Southern Hemisphere, they blow from the southeast. They are a feature of regular global atmospheric patterns.