Continue our tour of the four elements, we now come to the slipperiest, wettest one: Water.
Water names, especially ones derived from topographic elements relating to water such as Brooke, River, and Lake, but also other weather-derived names such as Rain, are pretty common in modern anglophone naming practices: But nature names like these are one of the few general categories of names which are distinctly modern. The evidence we have for water-elements in medieval names comes from three main types: compound names containing an element meaning or referring to water; names derived from named bodies of water; and names reference some water-based origin.
Of the first, we have, in England, the Old English word sǣ ‘sea, lake’, which was used as a prototheme in various compound names, both masculine and feminine. In our data, we have examples of Sehild (f.), Saulf (m.), Seaborn (m.), Seman (m.), and Serich (m.). Unlike other compound Germanic names, where the same themes show up in Germany, England, and Scandinavia, we have only found this element in English contexts with one exception — we have one example of a Swedish cognate of Seaborn in Finland (not yet in the dictionary: Sebijörs, gen.)
Of the second, we have Tiberius, a classical Roman name deriving from the river Tiber. Tiberius was the name of a Roman emperor, and, later, four Byzantine emperors. The name shows up in Germany and Italy quite early (most likely references to these emperors), and then there is a big gap before the name was revived in Italy in the 15th and 16th C, as part of the Renaissance fashion of mining classical names. In this context we should also mention the names Jordan (m., entry not yet available) and Jordana (f.). While the etymological root of the masculine name is almost certainly not the river in the Holy Land, the popularity of the name was significant increased because of its similarity to the river name, with many Crusaders returning with Jordan water and naming their children for it.
Of the final category are the names Marin (m.)/Marina (f.) and Pelagius (m.)/Pelagia (f.), Latin and Greek, respectively, for ‘of the sea’. In connection with Pelagius we should also note the name Welsh Morgan, which is etymologically unrelated to anything sea-like, but has historically been connected with Pelagius due to a false etymology of the protheme as deriving from Proto-Celtic *mori ‘sea’.