The toponym “Truso” is the oldest known place name from the area of the ancient tribal Prussians preserved in historical sources. In recent decades, several theories have been proposed trying to explain the origin of this name. One of these hypotheses sought to explain the origin of this toponym from the Lithuanian definition of salt – “druska” or its alleged counterpart in Old Prussian – “* truska”. However, the authors of this theory have not taken into account many of the factors which are discussed in this paper. The extinct Old Prussian language differs significantly from modern Lithuanian in terms of phonetics, grammar and basic vocabulary, as shown in this paper through the analysis of the vocabulary contained in the most important source on the Old Prussian language - the Elbląg Dictionary. Therefore, any transfer of words from Lithuanian to Old Prussian with the aim of “reconstructing” a word should be considered unacceptable. This is confirmed by the opinions of linguists concerned with linguistic reconstructions. The thesis that the equivalent of the Lithuanian term druska – salt was the Old Prussian word “*truska” is essentially incorrect. From the 16th century historical source (the so-called Dictionary of Grunau) we know that the Prussians used the word Sali (*sólis) for salt. This is also confirmed by another word from the 13th century Elbląg Dictionary (OP – E 376 Saltan) *saltań or “salted meat”. The etymological formula for the salt word in Old Prussian is therefore (IE) *sal- (1), (BALT-SL) *sālis – sól, (PBALT) *sālis – salt, (OP) *sólis (Sali) – salt. The word druska in Lithuanian literally means “crumb, scrap” (as in the related Latvian language) and was adopted into Lithuanian probably only in the Middle Ages - before the Lithuanians also used the word *sólis for salt. In this respect, the thesis claiming that the toponym of Truso originated from the neverpresent Old Prussian term for salt – * truska, is not supportable. This name cannot, in any case, be translated as Solec or “salt port”. The toponymTruso derives from a much older hydronim*Drusō or the Old Prussian name of the present lake Druzno near Elbląg.