When the Anglo-Saxons conquered Britain in the 5th Century, they transformed not only its society, but its language, which we now know as Old English. Remnants of their rule remain inscribed in maps of not only London, but Britain; the Anglo-Saxon suffix ‘-ham’ (as in Birmingham) meant homestead, for example, while ‘-ton’ (like Brighton) referred to a farm. The ending ‘-ing’, meant belonging to or associated with someone, or their followers. So Paddington was the farmstead belonging to Padda or his clan, Kennington was that of Cēna’s people.
When the Normans invaded in 1066, though, they seized Saxon properties to hand out among their loyalists and tacked on new names accordingly. One winner in the land-grab was the abbey of Bec-Hellouin, in Normandy, which was granted the land that once belonged to a Saxon chief named Tota. All of which turned into the name today, Tooting.
Around 190, London was Londinium.