Linguistic evidence is adduced indicating that (as non-linguistic evidence long known also suggests) the origin of Anglo-Frisian goes back to a period of common development in SE Anglo-Saxon England around 475-525. The linguistic reason to think so is that almost every characteristic innovation of Anglo-Frisian has a plausible motivation in terms of infl uences from Brittonic. It seems that the later Frisians originated as Anglo-Saxons, occupying territory between Kentish and Pre-Mercian, who left England and went back to the continent, of course to the coast, around 540. The conclusion is that Frisian is similar to English because Frisian is descended from English. Reasons to Th ink Th at Anglo-Frisian Developed in Britain 7 Reasons to Th ink Th at Anglo-Frisian Developed in Britain 11 But it appears that Germanicists have not taken the possibility of a Celtic origin very seriously, for it is clear that the word must be a recent borrowing from Celtic, more specifi cally Brittonic. Common Celtic had a word /lagu-/ 'little', from PIE /legʷh-/ meaning 'light (in weight)', cognate with Latin levis and English light. The similarity of meaning between /lagu-/ and AF /lais-/ is plain enough. The similarity of sound, though merely vague if we assume an old (and random) borrowing from Common Celtic, becomes quite a lot less so if we assume a recent borrowing from Brittonic. Four considerations, taken together, put a very diff erent light on things: 1) that /lagu-/, belonging to the fading /u/-stems, could easily be normalized as /lag-/, 2) that /a/ in Brittonic probably became /ae/ (see "the Low Vowel Complex" below), 3) that /s/ in AF /laeaes-/ could be by reanalysis of /s/ in superlative /-is-/ in Celtic, and 4) that intervocalic /g/ (before /i/) had been lenited to something like /ɣʲ/. This would get us as far as something like /laeɣʲis-/. Here the similarity of sound to AF /lais-/ is enough to raise severe doubts as to whether the similarity of meaning also seen is really just a coincidence.