The English ethnonyms "Jew" and "Jewish" originate from the Biblical Hebrew "Yehudi" (יהודי, meaning "Judahite," "Judean," or "one from the Kingdom of Judah") via the Greek "Ioudaios" (Ἰουδαῖος), Latin "Iudaeus", and most recently, the Old French "guiu" which dropped the /d/ sound (see, e.g., the Wikipedia page on the topic). I was curious if the loss of the /d/ occurred historically in similar constructs, or might this be a unique phenomenon to ostensibly exonymic usage, i.e. perhaps suggesting ethnic bigotry at the time the word developed (as one finds with many racial slurs in modern English, where only the first part of an ethnic name is used).
The loss of intervocalic -d- in Old French is a commonplace phenomenon.
So there's nothing to conclude from *ioudaeus > Old French guiu, which probably was pronounced zhüiv as present-day juive f. "(she) Jew". The form juif m. was created to disambiguize m. from f.
Note that your wikipedia source erroneously quote giu, a non-existing word. Should be guiu or in modern graphemics juiv.