The Humm Family of Belchamp Walter
The Humm family are recorded in the 1851 and 1891 censuses. A Mrs Humm also is reported as an attendee of the funeral of private Partridge in 1944.
There are two Charles Humms recorded in the Belchamp Walter burial register along with Ursula Humm.
Chapel Hill
The Humm family lived at 8 Chapel Hill in 1891. (BW Census 1891). Charles Humm is recorded to have been born in Wickham St. Paul's so there could be an indication of a move between the villages.
Making a search for "Humm Belchamp Walter" I find:

In keeping with many of the results that I find from Ancestry I need to take out a subscription to find out more.
The indication is that Martha Humm had one child from a marriage to a Firmin. This would make her Martha Firmin. She would have died before the 1891 census but the Firmin's do feature there.
Thomas Firmin was born in 1790 and this could have been the son of Martha Firmin (nee Humm).
A German Connection?
An additional search resulted in a list of Humms from the 18th century.
Again, this could have been a generated result from FamilySearch (Ancestry.com). I have a suspicion that there is some AI going on here.
The Geneanet record was generated 04.05.24 - The word "generated" makes me suspicious.