means A plant growing where it isn't wanted — or, in casual speech, cannabis — depending on whose garden and whose laws you're standing in.

from From Old English 'wēod,' meaning a grass or herb, with cousins in Old Saxon and Old High German. The word originally just meant a plant, with no insult attached; the scorn came later, as humans decided which green things deserved to stay. The slang for cannabis is a 20th-century American twist, leaning on the older sense of an unruly, fast-spreading plant. (Note: 'weeds' meaning a widow's mourning clothes is a separate, unrelated word, from Old English 'wǣd,' garment.)