In 13:24 we find the spies having arrived at Nahal Eshkol, cutting down a cluster of grapes, some pomegranates and some figs and carrying them away. The spot is called Nahal Eshkol based on the cluster (eshkol in Hebrew) they cut down. Interestingly, the passuk says, "אשר כרתו משם בני ישראל"
Bnei Yisrael did not cut the grapes down - the 12 spies cut the grape cluster down. That is such a significant incident that it gets the place named for it? And even so, why not say that the spies cut the cluster, why say bnei yisrael cut the cluster?
When you appoint a shliach - a messenger, a representative, that shliach is representative of you. When the shliach performs his duty, it is as if the sender is performing his duty. He takes the identity, to a certain extent, of the person sending him.
This applies to leaders as well. When you select a leader - a President, Prime Minister, etc. that leader represents the people behind him. When he goes and meets with foreign heads of state and signs treaties and agreements, it is not him making the agreement, but the nations he represents.
That is why here it says Bnei Yisrael cut the cluster from there. Sure it was only the 12 spies doing it, but they represented the nation. And since Bnei Yisrael cut the cluster, that is a significant event, deserving of renaming the location.