It is generally conceded that the first part of the word tatterdemalion (which dates to the early seventeenth century) is nothing more than tatter, or, more probably, tattered, “ragged.”
With respect to the second element, it has been suggested that it may have come from the French maillot, from Old French maillon, “swaddling clothes,” also, “an acrobat’s tights.”
However, most authorities agree that the second part of the word was coined from pure fancy, just as was the second part of ragamuffin, with which tatterdemalion is synonymous.