Well, summer has now ended, no more beach, no more swimming in the sea for me! Until next year, that is.
So, instead, it is time to investigate the word itself. Where does it come from? We have been using this word for a long time. In Middle English, a number of forms can be found, including sē, sǣ, seo, seea and the familiar sea. At that time, it referred not only to the sea as we think of it today; “large expanse of salt water covering much of the earth”, but also to lakes, pools and ponds, meaning “body of water of indeterminate size”.
However, its story in English does not start with Middle English. We can find it in Old English texts in the form sǽ, also referring to various bodies of water and not just the sea. Here is an example from the Anglo-Saxon version of Genesis:
God gecígde ða drígnesse eorþan and ðæra wætera gegaderunga hé hét sǽs
(God called forth water from the dryness and the waters formed the seas).
There are cognates in other Germanic languages, such as German See, Swedish sjö, Danish sø and Dutch zee, and from all of these a root has been traced in Proto-Germanic, *saiwaz, meaning “body of water”. It remains unknown where it comes from before that point.
The usual Proto-Indo-European word for sea is represented in English mere, with a wealth of cognates, from Latin mare to Welsh mor, to Russian more and others. Interestingly, however, rather than a derivative of Proto-Indo-European *mori- (sea), in ancient Greek it was αλς [als].