"that which is done, acted, or performed, whether good or bad, great or small," Old English dæd "a doing, act, action; transaction, event," from Proto-Germanic *dethi- (source also of Old Saxon dad, Old Norse dað, Old Frisian dede, Middle Dutch daet, Dutch daad, Old High German tat, German Tat "deed, thing done," Gothic gadeþs "a putting, placing"), from PIE *dheti- "thing laid down or done; law; deed" (source also of Lithuanian dėtis "load, burden," Greek thesis "a placing, setting"), suffixed form of root *dhe- "to set, place, put" (compare do).
In law, "written document authenticated by seal of the person whose will it declares, especially for the purpose of conveying real estate" is from early 14c. As a verb, "convey or transfer by deed," 1806, American English. Related: Deeded; deeding.