The vernal equinox occurs on March 20 or 21 and the autumnal equinox on September 22 or 23, marking the beginning of spring and autumn, respectively, in the Northern Hemisphere (and the reverse in the Southern Hemisphere). The days on which an equinox falls have about equal periods of sunlight and darkness.
In German, it’s called “meerrettich” (sea radish) because it grows by the sea. Many believe the English mispronounced the German word “meer” and began calling it “mareradish.” Eventually it became known as horseradish. The word “horse” (as applied in “horseradish”) is believed to denote large size and coarseness.