the.com/trade winds

means The steady easterly winds blowing from the subtropics toward the equator, reliable enough that sailing ships once set their routes by them.

from The 'trade' here isn't commerce directly — it comes from the older English sense of 'trade' meaning 'track' or 'path,' as in moving steadily in one direction, from a Middle Low German root related to 'tread.' A wind that blew 'trade,' i.e. constantly on course, became a trade wind. The commercial sense followed naturally, since these dependable winds were exactly what merchant sailing ships needed to cross oceans on schedule — so the name ended up fitting twice over, once by coincidence and once by consequence.