Analysis of information sources in references of the Wikipedia article "Io (mythology)" in English language version.
Afterwards she married Telegonus, king of Egypt, or Osiris, according to others, and she treated her subjects with such mildness and humanity, that after death, she received divine honours, and was worshipped under the name of Isis. [...] She is sometimes called Phoronis, from her brother Phoroneus.
Phŏrō-nis, ĭdis, f. adj., Phoronean, poet. for Argive [...] Subst.: Phorōnis, ĭdis, f., Io
On a étendu encore plus loin la signification de ce terme, & l'on appelle noms patronymiques, ceux qui sont donnés d'après celui d'un frere ou d'une sœur, comme Phoronis, c'est-à-dire Isis Phoronei soror.Summary/translation: "The term patronymic was expanded even further to include those named after a sibling, such as Phoronis to mean Isis, the sister of Phoroneus."