The Salmon

The salmon would have been a plentiful and nourishing source of food for the Indo-Europeans. At this time the fish would have swum in from the North Atlantic along rivers connected to the Baltic and would be quite easy to catch as they leapt up stream to their spawning grounds.

The fish still lives in Russia, around Scandinavia and the Baltic and in all these places it is known as some form of "laks-".
In Celtic languages, however, "laks" is not used. This can be explained by the fact that the Celts, migrating westwards, found a different variety of salmon on the river Rhine and gave it another name, replacing the original.

The English word salmon derives from Latin, probably from the word meaning to leap. In this way the Italic languages have Spanish "salmon' and Portuguese "salmao". The word "lax" or "leax" does appear before 1300 in Old English and in 1488 we read of "salmond laxis takin vp" (OED). It seems our joint origins in Celtic and Germanic language are demonstrated here.

In Greek and the Italic languages where there were no salmon the word fell out of use. In some other languages the word has changed its meaning such as in Tocharian, spoken in eastern Turkestan, where the word means fish in general.