Article: From 1898, it was commonly accepted that the name was of Celtic origin and meant place belonging to a man called *Londinos; this explanation has since been rejected. Richard Coates put forward an explanation in 1998 that it is derived from the pre-Celtic Old European *(p)lowonida, meaning 'river too wide to ford', and suggested that this was a name given to the part of the River Thames which flows through London; from this, the settlement gained the Celtic form of its name, *Lowonidonjon; this requires quite a serious amendment however. The ultimate difficulty lies in reconciling the Latin form Londinium with the modern Welsh Llundain, which should demand a form *(h)londinion (as opposed to *londinion), from earlier *loundiniom. The possibility cannot be ruled out that the Welsh name was borrowed back in from English at a later date, and thus cannot be used as a basis from which to reconstruct the original name.

Question: What is the meaning of the later-believed pre-Celtic Old European origin of London's name?
'river too wide to ford