An Etymological Dictionary of the German Language/Annotated/Lachs

by Friedrich Kluge

Lachs, masculine, ‘salmon,’ from the equivalent Middle High German lahs (plural lęhse), Old High German lahs; corresponding to Anglo-Saxon leax, Old Icelandic lax, Scotch lax; a common and primary Teutonic term for ‘salmon’; in Gothic perhaps *lahs. The Slavonic and Lithuanian words are cognate; Lithuanian lasziszà, Lettic lasis, Russian lososŭ, ‘salmon trout,’ Polish lasóš, ‘salmon.’ Hence the s in Old High German lahs is a suffix (compare Fuchs), and not a part of the root.