Why did they call the name of that place 'Nachal Eshkol/?
Seforno: Because the Cana'anim, who saw nothing special about the particular cluster of grapes that the spies cut to take back, 1 expressed surprise at the fact that they did so.
Targum Yonasan: They called it "Nachal - (the River of) Eshkol", on account of the wine that flowed like a river from the cluster of grapes that they cut.
Seforno: Seeing as there were numerous clusters just as big as it, and perhaps even bigger.
Seeing as the place was called 'Nachal Eshkol' when they first arrived (Pasuk 23), why does the Pasuk attribute the name to the cluster?
Rashi: The Torah calls it by the name that they eventually gave it, even though it was not yet called by that name. 1
Kol Eliyahu and Divrei Eliyahu: Initially, it was called by that name after Eshkol - one of Avraham Avinu's three close friends (Aner, Eshkol and Mamrei) - who owned it (Oznayim la'Torah). 2
Moshav Zekenim: When Moshe wrote this, it was already called 'Nachal Eshkol'. This is similar to 'Be'er Sheva', so-called on account of Yitzchak's covenant with Avimelech (See Rashi in Toldos Bereishis, 26:33), but the Torah calls it by that name even before that. See also Rashi in Bereishis 14:7.
Kol Eliyahu and Divrei Eliyahu; And this explains why initially, "Eshkol" is written Chaser (without a 'Vav'), whereas in Pasuk 24, it is spelt Malei (with a 'Vav'), since there was now an additional reason to call it by that name. Refer also to Bereishis 33:17:151:2.
Why was Nachal Eshkol named after the cluster of grapes, and not after the pomegranate or the fig?
Moshav Zekenim: Because the cluster of grapes was more significant.
Refer to 13:24:151:2.
Targum Yonasan: They called it "Nachal Eshkol" on account of the wine that flowed from the grapes like a river. 1
See also Na'ar Yonasan.
