What does Boxing Day have to do with boxing?
Old English græs, gærs "herb, plant, grass," from Proto-Germanic grasan (cf. Old Norse, Old Saxon, Dutch, Old High German, German, Gothic gras, Swedish gräs), from PIE *ghros- "young shoot, sprout," from root *ghre- "to grow, become green" (related to grow and green).
As a color name (especially grass-green, Old English græsgrene) by c.1300. Sense of "marijuana" is first recorded 1938, American English. Hawaiian grass skirt attested from 1937; keep off the grass by 1850.
Any of a large family (Gramineae or Poaceae) of monocotyledonous plants having narrow leaves, hollow stems, and clusters of very small, usually wind-pollinated flowers. Grasses include many varieties of plants grown for food, fodder, and ground cover. Wheat, maize, sugar cane, and bamboo are grasses. See more at leaf.
(1.) Heb. hatsir, ripe grass fit for mowing (1 Kings 18:5; Job 40:15; Ps. 104:14). As the herbage rapidly fades under the scorching sun, it is used as an image of the brevity of human life (Isa. 40:6, 7; Ps. 90:5). In Num. 11:5 this word is rendered "leeks." (2.) Heb. deshe', green grass (Gen. 1:11, 12; Isa. 66:14; Deut. 32:2). "The sickly and forced blades of grass which spring up on the flat plastered roofs of houses in the East are used as an emblem of speedy destruction, because they are small and weak, and because, under the scorching rays of the sun, they soon wither away" (2 Kings 19:26; Ps. 129:6; Isa. 37:27). The dry stalks of grass were often used as fuel for the oven (Matt. 6:30; 13:30; Luke 12:28).