Isabel (Portuguese, Spanish), Isabella (Italian), Isabelle (French) are women's names, formally translated into English as Elizabeth or Elisabeth but often substituted (in English) one for the other, seemingly arbitrarily. Spanish Isabel, for example, is often rendered into English as Italian Isabella and sometimes as French Isabelle but seldom as English Elizabeth or Elisabeth; for another example, both Isabella and Elisabetta are Italian names. The common modern English spelling is Isobel.
Opinion has long been divided as to the origin of the name but the strongest and most credible claim would appear to be that of 'Isis bella'. This was an expression along the lines of ‘God is Great’ or ‘Allah Akbar’ but with the bella (from bellus meaning beautiful) emphasising her femininity. While it is hard to be sure through the mists of time, it would appear that attempts were made to cleanse the name, remove its non-Christian origin and class it as a variant of Elizabeth. Wikipedia
