The reasoning went as follows: Since the term for Atlantic salmon in the Germanic, Baltic and Slavic languages could be derived from a common Proto-Indo-European root *laḱs, the urheimat of the Indo-Europeans must be where both the languages and the object it describes can be found: Northern-Central Europe. The argument was first put forward by German philologist Otto Schrader in 1883. The argument was subject to continued scholarly debate throughout the late 19th and early 20th centuries, particularly in German academia.
In 1953, German indologist Paul Thieme submitted that the descendants of laḱs- found in the Caucasus described the trout (Salmo trutta) rather than the Atlantic salmon (Salmo salar). American philologist George Sherman Lane concurred in a 1970 conference paper: "In my opinion, the name in question probably did refer originally not to the Salmo salar at all, but rather to the Salmo trutta caspius of the northwest Caucasus region." That lent support to the Kurgan hypothesis.
^Adams, Douglas Q. (1985). "PIE *lokso-, (anadromous) brown trout' and *kokso- 'groin' and their descendants in Tocharian: A coda to the Lachsargument". Indogermanische Forschungen. Berlin: Walter de Gruyter (90): 72–78.CS1 maint: ref=harv (link)
^Diebold, A. Richard (1976). "Contributions to the Indo-European salmon problem". In Christie, William M (ed.). Current proceedings in historical linguistics. 2nd International Conference on Historical Linguistics, Tucson, 12–16 January 1976. Amsterdam: North-Holland. pp. 341–387.CS1 maint: ref=harv (link)
^Giacalone Ramat, Anna; Ramat, Paolo (1998). The Indo-European Languages. New York: Routledge. ISBN978-0-415-06449-1.CS1 maint: ref=harv (link)
^Thieme, Paul (1953). "Die Heimat der indogermanischen Gemeinsprache" [The homeland of the common Indo-European language]. Abhandlungen der geistes- und sozialwissenschaftlichen Klasse. Mainz: Akademie der Wissenschaften und der Literatur, Wiesbaden (11).CS1 maint: ref=harv (link)
^Lane, George Sherman (1970). "Tocharian. Indo-European and Non-Indo-European Relationships.". In Cardona, George; Hoenigswald, Henry M.; Senn, Alfred (eds.). Indo-European and Indo-Europeans. Third Indo-European Conference at the University of Pennsylvania. Philadelphia. p. 83.CS1 maint: ref=harv (link)