An interest in place names of England takes most back to the Old English language spoken by the Saxons. However when it comes to river names these are often much older, from the Celtic culture of the pre-Roman era or even earlier tongues.
The very earliest languages prove a problem to define for they had no written form, at least nothing of which we are aware. Neither do we have the equivalent of the Rosetta Stone which enabled linguists to translate the hieroglyphics of Ancient Egypt. What we do have is related languages which are known, the surviving Celtic languages of Welsh, Gaelic, Breton and Cornish are closely related.
We also have a good understanding of Proto-Germanic - the mother tongue of English, German, Dutch, Danish, Norwegian, Swedish, and Icelandic languages - and Proto-Indo-European which, as the name suggests, is the hypothetical language which gave rise to all European languages, including those of Western Europe, Eastern Europe, the Middle East and the Indian Sub-Continent. If those seem quite unrelated it will come as a surprise to find evidence of words in Sanskrit and Welsh being quite similar in form and identical in meaning, especially when those words are as basic as meaning 'water' or 'river'.
Working through the names it soon becomes apparent that many river names are highly simplistic. A lot are not recognised because we are unaware of the meaning in the ancient languages, however it is not unusual to find these meaning simply 'water', 'river', 'strong', etc. Before dismissing these definitions as overly-simplistic, consider those who coined the names of these rivers.
Most likely these names are around two thousand or more years old. Travel at that time was very slow compared to today. Theoretically it is possible to traverse the length of the country in a car from Land's End to John O'Groats in a single day without breaking the speed limits. Of course this does not take into account fatigue, traffic jams, hunger and comfort breaks! In earlier days it is unlikely if the vast majority ever travelled far enough to see more than one or two significant rivers in their entire lives.
Normally the local river was enough for all their uses, that and the many springs and rivulets, brooks and streams which fed it was more than enough. While the small tributaries were manyfold and probably had different descriptions, the main water course (even if it did have a river goddess or other great significance) was probably rarely spoken of as more then 'the river'. Even today anglers will speak of going to 'the river' to fish, or perhaps a sunny afternoon will see a family take a picnic down by 'the river'. Notice how rarely locals use the name of the river in conversation.
Major rivers are lengthy. Most are much longer than our ancestors would ever travel under normal circumstances. As rivers are often named for the land through which they flow or, related to that, the age of the river is spoken of - young rivers are fast and noisy as they descend steeply, old rivers are sluggish and meander through flatlands. It thus makes sense to assume they were known by different names at different points along their course.
As the population was sparse and communication difficult, it follows that a river known for the oak trees growing along its banks at one point, would be known for waterfalls, or perhaps the eels known to be caught elsewhere. The names which we know today are probably down to the earliest cartographers asking the name of a river at a certain point. When they enquired as to the name of a town it was different, they don't move and are not potentially hundreds of miles in length.
So bearing all that in mind what of the most famous rivers in the land, that of the Thames? It's name is thought to be identical in origin to Tame, Teme, Tyne, Tamar, Thame, Team, etc, all derived from a single ancient source probably meaning simply 'river' although some argue it refers to the lower courses of these rivers where they would be aptly describes as 'the dark one'.
At Oxford it is well known that the Thames is known as the Isis which, for many years, was said to refer to the river goddess. Actually it is simple anomaly, the name is recorded as Tamesis in a document from 51BC and in later years locals mapping Oxford misunderstood this name and thought the river was the Isis. It has never been its official name in the city, although none would argue it should not be used.
Avon is a common river name and many will be aware it represents Welsh meaning simply 'river', Taff is a corruption of afon or Avon. Ouse is again 'water', while Ure, a tributary of the Yorkshire Ouse, has identical origins in 'water'. Wear is another meaning 'water, river', Wey has a root war 'water', with Wye being identical.
Sometimes the name goes a little further and describes the river's appearance in more detail. Hence we find Afton, from Scottish Gaelic for 'brown stream'; the Dove comes from dufan 'the dark or black one'; both Lea and Lee are Celtic for 'the light river', used in the sense of 'clear water'; Lune tells us the waters were 'healthy, pure'
Other rivers refer to the flow, such as in the case of the Aire, an Old Celtic name meaning 'the strong one'; the Axe, Exe, Esk, Usk all share a common origin in 'to gush forth' and all were clearly first named in the upper courses where the flow most swiftly; Ayr is thought to be a very early name meaning 'smooth-running'; the Clyde is a Brythonic clat or 'the cleansing one'; the Forth is from fioerth meaning 'smooth running'; Liffey is an Irish name meaning 'fast or strong runner'; Taw is a very ancient name and related to the Sanskrit tavas 'powerful river', Tweed has identical beginnings.
Not only do names describe the water itself but also the course taken. The Cam is found in several places, most come from a word related to Welsh cam meaning 'crooked'. That of the Cherwell combines Celtic and Old English to describe 'the stream in the hollow gorge'. The River Irwell is Old English for 'winding stream'. Sid is an Old English name meaning 'broad', the name must be comparative for this is never a broad river anywhere along its course. Trent is a Celtic name meaning 'the wanderer' and describing it as likely to flood. Yeo is an ancient Celtic name describing 'the forked river'.
Then there are those which refer, not to the water but to the land through which it flows. Cole is a common river name, it may have more than one meaning, depending upon the example, but most often would describes 'the hazel trees' which grow nearby. Other trees are seen alongside the Dart, this time it is 'the oak tree river'. The Derwent, despite the obvious difference, also describes the 'oak trees' which grown along its banks. The Mersey is 'the boundary river'. Spey is probably 'hawthorn river', suggestions of 'gush, spew' seem somewhat contrived.
Water had great spiritual meaning to the ancients. Considered another world many offerings were placed beneath surface of the water right through to Saxon times. Hence we find reference to the deities in the names of rivers such as Annan, which is from Anu, the Gaelic goddess of prosperity; the Dee represents 'the goddess, the holy one' and is likely related to the Latin dei 'God'; the Don in Scotland has identical beginnings; and the Irish Sea and the Shannon is associated with the river goddess Sionna.
Many names are created by the process known as back-formation. That is where the river has name taken from a place associated with it. The best example is that of Cambridge, where the name appears to refer to 'the bridge over the Cam', yet the original river name here was Granta.
Sadly some are simply too old or corrupt to be understood. Examples include the Colne in Essex, the Fal in Cornwall, Humber in Yorkshire, Medway in Kent, Orwell in Suffolk. The Severn is an enigma, a puzzle which has baffled and frustrated toponymists for decades. For many years it was said to represent Sabrina, a goddess of the river. However we now know this was simply a Roman idea and the real origin is unknown.
I would welcome any suggestions for themes or subjects, or even specific words to examine the origins, meanings and etymologies. I’d be delighted to hear from you.