or Dalmatic. A robe, open in front, reaching to the knees; worn at one time by deacons over the alb or stole, when the Eucharist was administered. It is in imitation of the regal vest of Dalmatia, and was imported into Rome by the Emperor Commodus. A similar robe was worn by kings, in the Middle Ages, at coronations and other great solemnities, to remind them of their duty of bountifulness to the poor. The right sleeve was plain and full, but the left was fringed and tasselled. Deacons had broader sleeves than sub-deacons, to indicate their duty to larger generosity; for a similar reason the sleeves of a bishop are larger than those of a priest. The two stripes before and behind were to show that the wearer should exercise his charity to all.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894