Anglo-Norman words a bliodgi:
So it rather looks as if the reflex of Anglo-Norman mucier found its way into English – and into written texts, only belatedly – with the central Anglo-Norman meaning of “to hide”, before undergoing semantic extension to cover also the idea of “to play truant”. Now, in modern English, that is its only meaning, and only in certain areas. The connection to “hiding” is probably lost because that core sense has fallen out of use, and it is highly unlikely that its French origin in mucier is known to truanting schoolchildren.
Mitch, like fitchew, belongs to that susbtantial number of English words which derive from Anglo-Norman, but from Anglo-Norman words whose French equivalent has now become obsolete. As a result, even English-speakers with a decent knowledge of modern French are unlikely to make the connection between the words they use, and their distant French (or Anglo-Norman) ancestors. Thus is lost not only part of the history of English, but also part of the story of the role, and the extent, of Anglo-Norman as an influence on English.