What does Boxing Day have to do with boxing?
"watercourse," 1839, from Arabic wadi "seasonal watercourse," prop. participle of wada "it flowed."
a dry channel lying in a semiarid or desert area and subject to flash flooding during seasonal or irregular rainstorms. Such transitory streams, rivers, or creeks are noted for their gullying effects and especially for their rapid rates of erosion, transportation, and deposition. There have been reports of up to 8 feet (2 m) of deposition in 60 years and like amounts of erosion during a single flood event