1888 in reference to winds generated convectively from a downburst cluster, from American Spanish derecho "direct, straight ahead" (also "right, justice"), from Old Spanish diestro, from Latin directus "straight," past participle of dirigere "set straight," from dis- "apart" (see dis-) + regere "to direct, to guide, keep straight" (from PIE root *reg- "move in a straight line").
When, years ago, I first called public attention to this kind of straight blows peculiar to Iowa prairies in summer, I named them provisorily Iowa squalls. The term derecho, coined from the Spanish in analogy with the term tornado, and expressing the main feature of a straight blow, has been chosen to bring out the contrast with the tornado or whirl-wind to avoid further confusion of these two different storms. [Gustavus Hinrichs, "Tornadoes in Iowa," in Report of the Iowa Weather Service for the Year 1888]
updated on July 29, 2018