It is true that it came to an end about 1400, when it ceased to be spoken; but at an earlier date it was alive and vigorous, and coined its own peculiar forms.

A very simple example is our word _duty_, which certainly was not borrowed from the Old French _devoir_, but from the Anglo-French _duetee_, a word familiar in Old London, but absolutely unknown to every form of continental French.
The point which I have here to insist upon is that not only does our literary language abound with Anglo-French words, but that they are also common enough in our dialects; a point which, as far as I know, is almost invariably overlooked.

Neither have our dialects escaped the influence of the Central French of Paris, and it would have been strange if they had; for the number of French words in English is really very large.

It is not always possible to discriminate between the Old French of France and of England, and I shall here consider both sources together, though the Old Norman words can often be easily discerned by any one who is familiar with the Norman peculiarities.
Of such peculiarities I will instance three, by way of example.

Thus Anglo-French often employs _ei_ or _ey_ where Old French (i.e.of the continent) has _oi_ or _oy_; and English has retained the old pronunciations of _ch_ and _j_.