They were considered to share a common origin either in Proto-Indo-European or in the younger proto language of the so-called "Litu-Slavo-Geramans"[9] The occurrence or absence of those words was thought to provide clues for the Indo-European urheimat.
Some of the numerous hypotheses about its location e.g., in Northern Europe, in the Kurgan, or in the Balkans, were based on race theory[10] or nationalistic ideas.
[15] When it comes to salmon (Latin: Salmo salar), dictionaries being published from the 1970s on began to compile more and more similar words for it in Germanic, Baltic, and Slavic languages.
[19] Since Schrader thought this to be the origin of the Germanic people only, he did not introduce this argument in the discussion about the Indo-European urheimat.
The anthropologist Karl Penka, who believed the urheimat to be in South Scandinavia, wrote about salmon in 1886, "this fish was known to Arian people," without stating, how he came to this conclusion.
Neither does it occur in the rivers of Asia and the Mediterranean, therewith explaining the absence of corresponding forms of Proto-Indo-European *lakhasa in the Iranian and Indic languages, Greek, and Latin.
The urheimat debate was based on the words for plants and mammals, agricultural terms, archeological findings, and craniological comparisons.
[26] The textual fragments of this language were mostly from the second half of the first millennium AD and were written in two different variations, which were later called Tocharian A and B.
"[30] He pointed out that salmon species do occur in Caucasian rivers, Indologist Sten Konow noted its similarity to the Tocharian word.
Even after the fall of the national socialist government in Germany, the salmon argument kept being controversial for the identification of the urheimat.