I found several sites (in Portuguese) which say that Natércia was coined as an anagram of
Caterina by Luís de Camões, a Portuguese poet in the 16th century, to hide the true name of his girlfriend
Caterina, e.g. here:
http://inforum.insite.com.br/fernandopessoa/8309769.html
Interesting. If true, this would be the first such "anagram" case that I ever heard of (just reading things backwards does not count.)