The Fool is actually one of the oldest elements of the morris, even older than, for example, the use of sticks and hankies. In the late Middle Ages, one popular form of morris was a narrative dance where a lady had to choose between a number of different types of man. The Fool was one of these, and he and the Lady (later a man in women's clothes) survived in morris after the dance and the story parted company.
A Fool always carries some kind of staff of office and by the C19th
century the traditional form was a blown-up pig's bladder on a stick,
which was used to whack dancers and audience alike. Pig's bladders are
quite hard to get hold of nowadays, and frankly, none of us (least of all
the Fool!) fancied the disgusting job of preparing one for morris use.
Think what you have to empty out of it ... quite. The feather duster, we
reckoned, is the modern equivalent, and anyway, people much prefer a
tickle to a whack.
We're often asked if the tickle is 'lucky' - if that's what you want to believe, go ahead! (Just don't sue us when it doesn't work.)
No! It doesn't really belong with Cotswold Morris at all, but when we were trying to decide what our Fool should wear, she happened to be trying on a coat belonging to a Mummer and realised it would be just the thing. All the little bits and pieces were added on because she was a Christmas tree in a previous existence - there is no meaning or symbolism attached. Sorry!
They're traditional - many, probably most, morris Fools wear them. They are a survival from the court Fool costume, which is believed to be a satire on a late mediaeval fashion for parti-coloured clothing. And no, they're not tights, and no gentleman would dream of enquiring further.