G'day Pierre,
so are you "sitting on the fence" like me?
a few comments:

Yes Ceader (cedar) Isle, referring to those tiny islets

- in the center of the map : "Ceader Ile" [Ceader Island] unless it is
"Ceader Fle" an abbreviation of Fleuve ???
I am uncertain of this 1st letter I or F ???
-also on the left : "Sharpes Ile"

On the two large estuaries Powhatan & Pamaunk, "flu" is followed by the
sign ":" meaning an abbreviation ???

Yes I noted that, the horiz punctuations mean abbrev, but for what

But I also like Robert's explanation : latin - especially in Science -
was / is still used as a common language in many cases (like now in
botanic sciences).

Me too! seems logical, but logic sometimes bites us on the snout!