I assumed it was short for Jebediah. Which I think isn’t an uncommon misconception, google search for ‘Jebediah Bush’ brings up a lot of hits that all seem to relate to the politician. I associate that name with sorta cowboy-film times and places but it didn’t seem inconceivable that a guy his age would still be called that.
There is a weird sorta dual stereotype of American boys’ names in the UK I think.
On the one hand, we expect Americans to be more likely to have short modern-sounding names like Chuck*, Chad, Chase, Tyler, Troy, Buck**, Todd, Hank, Dale, Chip**, Brett, Corey, Kyle.
(* I think this is more a nickname for Charles that isn’t used much outside the US? But it is also some people’s legal name, and I think we do also have a stereotype that Americans are more likely to have a shortening or nickname as their legal given name.)
(** I don’t know to what extent these are likely to be nicknames, not given names.)
On the other hand, I think we also expect some names we would consider quite long and/or old-fashioned to come up more: rarer Biblical names, for instance, particularly those ending in ‘-ah’ or ‘-iah’ (Jebediah, Jeremiah, Elijah, Josiah, Obadiah, Zachariah), as well as surname-as-first-name ones like Jefferson, Finnigan, Langdon, Bryant, Henderson, Harrison, etc.
Of course the surname-as-first-name thing also applies for girls, and also explains*** some of the shorter, modern-sounding names, such as Bryson, Sawyer, Mc- and Mac- names, Brady, etc.
(*** I believe even the ones that are place names are often surnames as well, and in the US it seems likelier that they were surnames first, and the place was named after a person. In the UK, it may be more likely that it was a place name that became a surname - ‘John of Wakefield’ becoming John Wakefield, etc - which, of course, is how the family of the person the place was named after may have come by it.)
I think this might follow the pattern of many stereotypes? Which is to say that the list of most popular boys’ names (in Anglophone families at least) in both countries over the last century or so would mostly consist of the same old standards like John and Alexander and Thomas and so on, with some shared and some differing trends over which are most popular at which times. But, if you were to isolate the names that have a large gap in prevalence between the two countries - the most distinctively USian names - they would conform roughly to the stereotype.
This is conjecture, though, I don’t actually know. I also imagine doing that would bring up names common to ethnic/cultural groups that are much more numerous in one country than another? A greater proportion of Joses in the US and Mohammeds in the UK, etc.
I mean, looking at my list of Biblical names above, they all look pretty Old Testament, which makes me wonder if there’s a link to the size of the Jewish population - but my instinctive associations for a USian Jebediah or Zachariah is that he’s either a salt-of-the-earth working-class background character in a movie about cowboys or the Gold Rush, or his full name is Jebediah D. Rutherford III and his family made their fortune back when you didn’t have to pay your plantation workers. Neither of which feels very Jewish, as stereotypes go.
(Epistemic status: I know very little about any of this. I just find it interesting. I definitely don’t know how names actually are in the US to any degree beyond ‘I can google the popularity of names’, and I’m only reasonably sure I know what UK stereotypes of USians are like, if that makes any sense. These are the stereotypes I have observed from the media and people I have come into contact with, and as such may not be representative of UK stereotypes about USians in general.)