DOST

dost  'friend' was one of the first few Hindi words I encountered, and like so many words in Hindi, it has been borrowed from Persian (in Modern Persian it has become dust, as far as I know).

I don't know in how many contemporary languages it has become a loanword as well, but at least I often read it in Turkish internet posts.

Its meaning alone makes me love the word – but for a person interested in historical linguistics, there is a lot more to it – a long history dating back to, roughly estimated, 3,000 BCE, and a rich variety of descendants of the original Proto-Indo-European word in various Indo-European languages.

But how can we know that word and what it meant?

First, we can go back to the Old Persian language, to the inscriptions of King Dareios. With the word dauštar   'friend', the predecessor of dost, Dareios seems to have spoken of his true allies, as opposed to the „liars“, those who betrayed him.

In the most ancient layer of the Sanskrit language, called Vedic, we have a word that is phonetically corresponding to dauštar : joṣṭár 'loving'. As the two meanings can also easily be related to each other, we can be sure there must have been a word that is the common predecessor of both.

Most likely, that predecessor wasn't a noun, but a cognate verb. As we can tell from the suffix -tar-, which is common to both nouns, these words are agent nouns derived from a verbal root.

That verbal root in fact exists; it is to be found in Old Persian as well as in Old Avestan (the language of Zoroaster), and also in Vedic Sanskrit:

The Old Persian verb is dauš-, the Old Avestan cognate being zauš-, and the Sanskrit word is juṣ-.

The three verbs share roughly the same meaning: ENJOY.

Looking closer into the Sanskrit texts, it becomes clear that 'enjoy' isn't just meant to be a passive emotional state elicited by a pleasurable sensation, but a feeling evoked by something or someone that has been CHOSEN.

By looking back even further in time (plus by comparing cognates from even more Indo-European languages), at last we find the Proto-Indo-European (PIE) verb *ğeus- 'to taste', 'to relish'.

After that most ancient PIE stage (which we can only deduce, of course), the Indo-Iranian branch wasn't the only one in which that verb was preserved in several ways.

In our Germanic languages, Old English ceosan 'choose', 'taste', 'try' has originated from Proto-Germanic *keusanan (cf. Dutch kiezen, Old High German kiosan, German kiesen, Old Nordic kjosa , and the like in other Germanic languages), which of course has descended from the same PIE base *ğeus-, and has eventually become our choose (somehow choice is also related to it, btw).

The Romance languages have preserved that ancient Indo-European verb as well. Latin gustare 'taste', 'take a little of' is cognate to the verbs discussed above and a descendant of *ğeus- ., with several modern verbs (and nouns) originating from it, e.g. Spanish gustar.

It is obvious that the semantic development of the root takes various directions in the respective language families, may it be 'choose' or 'try' in the Germanic languages, and often 'taste' in Romance.
So English choose, Persian/Hindi/Turkish dost  and Spanish gustar  (plus many more words in other languages) all originate from a common ancestor, the PIE word *ğeus- 'taste', 'relish'.
 
Because it fits with this post in a way, at last a link to a wonderful song: Manu Chao, Me gustas tú