Rivers and Romans
Our river names are some of the oldest names still in use today. Because it was customary for the Romans to assign local names, usually the names of rivers, to their forts we know what the names of those rivers must have been before they arrived.
For example, Segontium was the fort on what is now the river Saint or Seiont in Caernarfon, Canovium was on the river Conwy, Deva on Dyfrdwy or Dee and Tamion was the name of the Roman fort on the river Taff in Cardiff
The Taff belongs to a group of Celtic and European river names all meaning something like 'flow' (although it was once believed to mean 'dark'). In that group are, for example, the rivers Tawe, Teifi, Team, Tame and Thames. It is interesting to note that Cardiff, Swansea and London are on rivers with the same linguistic source.
Place names containing the element 'aber'
An element usually comes before the name of the river in place names, as in Castell-nedd (Neath) and Llanelwy (St Asaph). We connect names including nant (stream), blaen (source of a stream), glan (bank), rhyd (ford), ffynnon (well) with rivers, but the most common element in this context is aber.
Aber (estuary) means either a place where a river flows to the sea, or where a smaller river flows into a larger river. The river Daron flows to the sea at Aberdaron, for example, and Aberhonddu (Brecon) describes the place where the river Honddu joins the river Usk.
Someone could easily think that the town of Aberystwyth is on the banks of the river Ystwyth, but that would be a mistake. Aber Rheidol would be a more accurate name for the town today.
A castle was constructed in 1110 about a mile and a half to the south of the present castle, on the bank of the river Ystwyth, so it was natural to call the castle Aber Ystwyth. In 1211, when another castle was built on the bank of the river Rheidol, which became the focus for the modern town of Aberyswyth, the old name was retained.
Perhaps the names Berffro and Bermo, which by now are acceptable Welsh forms of Aberffraw and Abermawdd, are also misleading. Neither the element aber nor the names of the rivers Ffraw and Mawdd are obvious in the names we use today.
The name of a river usually follows the element aber, but this is not always true. Sometimes a landscape feature occurs rather than a river name, as in Aberglaslyn and Abergwyngregyn.
The old meaning of the masculine word, nant is 'valley' as in Dyfnant (deep valley) - now Dynfant near Swansea. Today, the feminine word nant means 'small river' so care must be taken before assuming that flowing water can be found in a place which includes this element.
The element blaen, which refers to the upper reaches or source of a river, has a similar story. Because the source of a river is usually in mountainous land, blaen or blaenau are also used for highland.
You would be excused for not spotting the element glan (bank) in some place names. For example, in the case of Llancaeach and Llanbradach, glan is in fact the first element, although it has been replaced by llan. Caeach and Bradach are the names of streams.
Gods and goddesses in river names
The names of gods and goddesses are also very apparent in river names. The name of a battle goddess occurs in the river Aeron - aer (battle) and the suffix -on. The same suffix occurs in Aberdaron, which refers to the goddess oak (derw).
There is also a divine connection in the name of river Dyfrdwy (Dee) - dwfr (water) and the element dwy(w) (goddess), as in Dwyfor, Dwyfach and the Dee in Scotland. It is likely that the goddess in questions here was Aerfen, the goddess of war. Llyn Tegid (Bala Lake) is called Llyn Aerfen in medieval literature.
It is thought that Alaunos, the name of an old Celtic god who may correspond with the Roman god Mercury, is the source of the name. It is possible that al- means winding. This element also ocurs at the beginning of the names of the rivers Aled and Alwen.
The descriptive nature of river names
We can often get an idea of the nature of a river from its name.
We get an impression of how wild a river's flow is from the names Abergarw and Nantgarw near Taffs Well. Although the element bryw is concealed in the name Bronant today, the liveliness and energy of the stream is reflected in the original name - Briwnant. The name survives to the present day as the name of a house in the village.
The sound of a river is also apparent in a number of river names. For example we get an obvious suggestion of the babbling of the river Llafar (literally 'vocal'), and also from the river Ieithon, which derives from the word iaith (language).
In contrast some names reflect the tranquility and calmness of a river.
For example the river Llyfni, which is the word llyfn (smooth) with the suffix -i. Honddu derives from the adjective hawdd (easy) in the meaning pleasant or leisurely.
It is likely that -wy is the most common suffix in the names of places with rivers. Its meaning conveys a river's winding meander. It is often shortened to -w, especially in areas under the influence of English.
Animals in river names
It is not unusual to find the names of creatures in a river name, which shows how sacred animals were considered to be. The river is often seen as similar to the pig family, furrowing through the earth. Take for example Abersoch. The element soch is related to the Irish word for pig socc, which occurs in the name of the river Suck in Connacht.
The river Twrch (literally 'hog') in Ystalyfera and Llanuwchllyn are other examples, as is the river Hwch (sow) near Llanberis. Banw, a word for a 'piglet', is apparent in the river names Banw in Montgomeryshire and the rivers Aman (from Amanw) and Ogwen.
References to tools and weapons
We often see a reference to tools and weapons in the names of our rivers which conveys the act of cutting through the land or the depth of the river. It can also suggest the brightness of the river. For example a colloquial form of gelau, which means a 'pike' or 'blade' occurs in the case of Abergele, although some have wrongly interpreted it as a form of gelen (leech).
The same idea occurs in Aberdaugleddau (Milford Haven). There are two Cleddau rivers - Cleddau Wen and Cleddau Ddu, and both rivers, or metaphorically both swords, meet there to flow to the sea. The element og, which occurs in Ogwr and Ogwen, also mean something sharp or fast.