One of the biggest questions about the North Germanic languages concerns their words for the sun: solen and sólin. They are just too similar to the Latin solis. Something similar happens with Sól, the Sun personified in Norse mythology. These are all just like the Latin word for sun. What gives?
Let’s embark on this etymological journey to find out what is going on.
In English we use the word sun for the big star shining from the centre of our solar system. This is a Germanic word.
Some other West Germanic languages also have similar words for the sun, as is normal with members of the same language family, like for example the German Sonne, the Dutch zon or the Frisian sinne. Even the distant Gothic language, from the East Germanic branch, had sunno.
Looking at some Romance languages we can find words with a completely different root, as expected, like the Spanish Sol, the French soleil or the Italian Sole. It is well known that these originate from the Latin solis.
This root however is not unique to the Romance languages. If we take a look at the North Germanic languages, we will find it there, too: Solen in Norwegian, Swedish and Danish and Sólin in Icelandic.
And if we look into mythology, the Goddess Sól of Norse mythology bears a very similar name to that of the God Sol of Roman mythology.
Now, the first question that pops into mind is: are these words loanwords from Latin? Well, simply put, no. No, they are not. Let me explain.
It has been theorised, both the Latin and North Germanic root sol- could have evolved from a possible Proto-Indoeuropean *séh₂w-l. At the same time, the other Germanic variant sun- could have come from a possible Proto-Indoeuropean *sh₂u-én-.
These two would have meant sun and, actually, they would have even been the same word. Well, to some extent. This is what we call a heteroclitic word.
A heteroclitic word or noun will alternate between different stems depending on the case. Let’s stay with our Proto-Indoeuropean words for sun to keep it simple.
It is believed the word for sun in Proto-Indoeuropean would have alternated between a form with -l- and another one with -n-. The first one would have been a nominative form while the latter would have been an object case.
An object case, sometimes referred to as an oblique case, is used for everything except for the subject of the sentence, while the nominative case is used for the subject. We have this in English, actually- with the pronouns.
When we use a pronoun as the subject of a sentence we use I, he, she, we and they but these will turn into me, him, her, us and them in other cases (pun not intended), like when they become the direct object or the indirect object of the sentence. The first set of pronouns is in the nominative case while the second one is in the object case. These are not heteroclitic, though.
With that said, we can say that the nominative root *séh₂w-l would have given us the Latin and North Germanic words and the oblique *sh₂u-én- would have ended up giving us the other Germanic words.
Now a good question to ask would be, how are we so sure about the North Germanic sol- words not being loanwords from Latin? They could very well have been.
While this is a good point, it can be explained by just looking at older Germanic languages. We can find similar words that differ quite a bit from the Latin sol and can be traced back to an older form and these ones can then be traced back even further to a common ancestor alongside Latin. Some examples would be the Gothic sauil (sun) or the Old English sol (sun) and swegl (sky, heavens, the sun).
That can be further corroborated by looking at other languages outside of the Romance and Germanic branches and tracing them back to a common ancestor, and like said before, these can later be traced back even further, alongside the Latin and the Germanic words.
The Lithuanian saulė, the Greek helios, the Old Church Slavonic slunice, Welsh haul, the Old Irish suil (eye), etc. all of these show us that the Latin and the North Germanic languages are not the only ones with the root sol-, therefore, a common ancestor is more plausible than words having been borrowed.
Wrapping up, I’d like to mention how amazing all this is- how words can sometimes be so intertwined that telling them apart becomes such a difficult task.
Some words might look like loanwords at first sight, while they are not. Some other words might look completely unrelated, when in reality they are closer than what we would expect. And there are always some, whose origins are still unknown.