Hint: The Coriolis force generated due to the rotation of Earth acts as a deflective force to the wind direction. Because of this force, all the winds are deflected to the right in the Northern hemisphere while they are deflected to the left in the Southern hemisphere with respect to the rotating Earth.
Trade winds are steady currents of air blowing from the subtropical high-pressure belt towards the equatorial low-pressure belt but the permanent winds blowing from the subtropical high-pressure belt to the subpolar low-pressure belt in both the hemisphere is called westerlies Under the influence of the Coriolis forces, they flow from the North-East in the Northern hemisphere and from South-East in the Southern hemisphere but the general direction of the westerlies is South-west to North-East in the Northern hemisphere and North-west to South-East in the Southern hemisphere.
Trade winds blow between 30° North and 30° South latitudes but the westerlies blow between 30° and 60° on either side of the equator. Because of the dominance of the landmasses in the Northern hemisphere, the westerlies become more complex and complicated and become less effective during the summer season and more vigorous during the winter season. The westerlies become more severe in the Southern hemisphere because of the lack of land and dominance of oceans. The name ‘Trade' is derived from a nautical expression ‘to blow tread' meaning to blow along a regular path or ‘tread’ but the belts of the westerlies move North and South following the Sun’s movement. There are known as westerlies because they blow out of the west.
Note: The velocity of the westerlies increases Southward and they become stormy so they are called roaring forties between latitude 40°-50° South latitudes, furious fifties at 50° South latitude and screaming sixties at 60° South latitude. Trade words came from nautical expression.