The neutron was named by the person who discovered it, James Chadwick.
According to the provided reference:
The essential nature of the atomic nucleus was established with the discovery of the neutron by James Chadwick in 1932 and the determination that it was a new elementary particle, distinct from the proton.
This clearly states that James Chadwick discovered the neutron. It is reasonable to assume that the discoverer of a particle would also be the one to name it. While the exact process of naming isn't detailed in the reference, the connection between discovery and naming is implicit.
