Some claim that Jebediah is a Hebrew name.
Is it a Jewish name?
Either way; what does/would it mean, and how is it/would it be spelled and pronounced in Hebrew?
Looking at several baby naming websites, you will find that Isaac is correct. The meaning given to the English name Jebediah is given as "Friend of the Lord," or in Hebrew ידיד י-ה.
Even the sites that do not source it as a variant of Jedediah explain its meaning this way - see here.
Regarding Jebediah being its own term, Malbim does not have such a word as יבד, nor does the Etymological Dictionary based on R' Hirsch (sorry, I don't see an online copy that goes that far into the book). The word does not appear in Tanach, although I only checked for the three letter shoresh. Thus, "Jebediah" appears to not be a Jewish name.