If, as Rashi explains (citing Onkelus), "Eil," "Eilonei," "Kikar," "Aveil" and "Ba'al" are the names of the particular plains (and not synonyms of "Meishar" [plain]), why does Onkelus translate each one as "Meishar," without stating their names? Moreover, how do Rashi and Onkelus know that all the above were plains or tall mountains? And finally, Mamrei is the name of a person, not of a location?
Ramban: "Eil Paran" was a location where rams (Eilim) were to be found, and "Eilonei Moreh," one where oak-trees ("Alonim") abounded (both of which one would find in valleys - even though both may well be place names). "Kikar," on the other hand, means a plain, as does "Aveil" - the former, a place where rivers flow, the latter, a desolate piece of land, which contains neither trees nor buildings. 1
Ramban does not discuss the term "Ba'al."
QUESTIONS ON RASHI
Rashi writes: "The plain of Paran is called 'Eil;' the plain of Mamrei is named 'Eilonei;' the plain of the Yarden is called 'Kikar'....."How can we prove that these are the specific names of these locations (and not just synonyms for "plain")?
Gur Aryeh: Why would the Torah use so many words for the same concept? (Rashi waits to point this out on our verse, for the Torah has now used three different words for "plain" in the span of 15 Pesukim!) Rather, each of these names is specific to a particular location. 1