My dictionary (Chambers) marks guiser as (Scot.) and also gives guisard. These it glosses by the equally evocative word mummer. However, Alan Garner wrote a book The Guiser, I think of short stories, folk tales. I'm a huge Garner fan but to my shame I haven't read this. But he's very much a Cheshire writer, so I'd expect his use of 'guiser' to be local for him.
The splendidly snappy word geezer is a variant of 'guiser' too.
The root is wise, meaning 'way, manner', as in 'in this wise' and 'clockwise'; taken from Germanic into French with the usual change to a gw- sound. (I always wonder if that was Breton influence.)
A guise is a way of behaving, a manner or mannerism, an external appearance: and thus by extension such an appearance that one is capable of adopting or dissembling or dis-guising.
Well I enjoy language. :-)
