Igor Dyakonov and Vladislav Ardzinba identified these hypothetical languages with the Samarran culture.
[1] Benno Landsberger and other Assyriologists argued that by examining the structure of Sumerian names of occupations, as well as toponyms and hydronyms, one can suggest that there was once an earlier group of people in the region who spoke an entirely different language, often referred to as Proto-Euphratean.
Terms for "farmer", "smith", "carpenter", and "date" (the fruit) do not appear to have a Sumerian or Semitic origin.
[vague] Dyakonov and Ardzinba proposed a different term, "banana languages", based on a characteristic feature of multiple personal names attested in Sumerian texts, namely reduplication of syllables (as in the English word banana): Inanna, Zababa, Chuwawa/Humbaba, Bunene, Pazuzu, etc found in Sumerian, Akkadian, Assyrian and Babylonian texts.
[2] Rubio challenged the substratum hypothesis, arguing that there is evidence of borrowing from more than one language.