I am just going to confuse things a little bit more (I'm a historian, it's sort of what we do); just as the W might actually be an inverted M, so the R/N (10th letter) might be an inverted I-S contraction. This letter does jump out as being different from the rest - it doesn't look like the N (1st letter) or the R near the end. And we do see contractions like it on, for instance, the sword from Alphen. Food for thought. In a more general sense, the inscription might have been a mystery even in the time when the sword was made - it adds to its 'magic', in a way. Perhaps only the craftsman who made it and the person who it was made for truly knew what it meant. Perhaps that is also why many of these swords were 'put to rest' in a river - it's dangerous to have such magical objects just lying around, after all. As an aside, I have studied Historical European Martial Arts myself and while a sword is certainly a tool, it is also a symbol. They can have both a practical and ceremonial use, one does not exclude the other.

Having studied similar swordblades from across Europe and specifically a recent find from Holland, it is almost certainly Latin. The inscription on the Dutch sword is rather similar, if longer and on both sides of the blade: +BENEDOXOFTISSCSDRRISCDICECMTINIUSCSDNI+ +DIOXMTINIUSESDIOMTINIUSCSDICCCMTDICIIZISI+ Since the Dutch sword refers to Saint Martin (MTINIUSCS), the same might be true of the River Witham sword - imploring a specific saint for protection or aid. In my opinion, the River Witham inscription can be read like this: +ND XOX CH WDN CH DXO RVI+ The first two letters implore Our Lord (Nostrum Dominus, or Nomini Domini - in the name of the lord). The next three also appear in the same position on the Dutch sword and most likely refer to the trinity in some way, or to Christ. The CH combination is interesting as it appears twice (and not one C and one G - same style of inscription appears on the Dutch sword). In between these two letter combinations are the letters WDN - perhaps the saint being implored? The DXO might again refer to God, Christ and the Holy Ghost. RVI might then refer to the owner or maker of the blade. As an aside, the lettering is incredibly similar to the Dutch sword in style. The decorations and flourishes are almost exactly the same. Details like the slightly rounded Xs make me suspect the two sword might even have been made in the same workshop. There is a sword in Berlin with similar inscriptions again. http://www.ad.nl/ad/nl/1012/Nederland/article/detail/3715518/2014/08/08/Mysterie-van-Alphens-zwaard-na-12-jaar-ontrafeld.dhtml Article on my research, in Dutch.