Why 'cyclopedia' not 'encyclopaedia'?

[fajfall]

Found a wonderful 'cyclopedia', 5 books long, of characters in fiction. Why isn't it called the 'encyclopaedia of fiction characters' rather than 'cyclopedia of fiction characters'? Why use one term rather than the other?

[Dreamwoven]

They are essentially the same, at least according to my Chambers English Dictionary.