The headword phrase, in the accusative case, is taken from Homer, Iliad 17.330 (in a phrase addressed to Aeneas by the disguised Apollo). It is glossed along similar lines in the scholia there, and in other lexica and grammars; references at Photius upsilon108 Theodoridis. However, deriving u(perdeh/s like this from de/omai "I lack" makes a poor fit in the context (unless the kai/ in kai\ u(perde/a dh=mon e)/xontas is concessive: "even if..."), and the etymological link may instead be with de/os "fright" (delta 246), as Eustathius suggests; see LSJ s.v.