"ragged child, person dressed in old clothes," c. 1600, probably from tatter (n.), with fantastic second element, but perhaps also suggested by Tartar, with a contemporary sense of "vagabond, gypsy."
Entries linking to tatterdemalion
tatter n.
c. 1400, tatrys (plural) "slashed garments," from a Scandinavian source such as Old Norse töturr "rags, tatters, tattered garment," cognate with Old English tættec, tætteca "rag, tatter." Related: Tatters.
tartar n.
"bitartrate of potash" (a deposit left during fermentation), late 14c., from Old French tartre, from Medieval Latin tartarum, from late Greek tartaron "tartar encrusting the sides of wine casks," perhaps of Semitic origin, but if so the exact source has not been identified; Arabic is unlikely because of the early date of the word in Latin. The purified substance is cream of tartar. Used generally in 17c. of encrustations from liquid contact; specific meaning "encrustation on teeth" (calcium phosphate) is first recorded 1806.