COULDWELL and COLDWELL are the same family and both are covered in this website.
CALDWELL is a different family and is not covered.
In early documents, such as parish records, written prior to the standardisation of spelling, the name COLDWELL is often found with different spellings (see examples below) but which still refer to the original Coldwell family. Many of these mis-spellings do not survive but sometimes a new spelling becomes everlasting and a different family surname is created. (Some genealogists call this a variant of the original surname).
The chief example of a new surname which started out as Coldwell is probably COULDWELL which is common in the Sheffield area of Yorkshire, England. Couldwell appears to be a variant of Coldwell. This website treats Coldwell and Couldwell as the same family – that implies that both surnames originated from the first male person to be named Coldwell (or its equivalent original spelling) when surnames first came into common usage in the 12th century. That person is sometimes referred to as the progenitor of the family.
Sometimes surnames can arise in different places with different progenitors, but it likely that in the case of Coldwell there is only one origin, that is, the Coldwell family located in the Holme Valley region near Huddersfield, Yorkshire, England.
In the local Yorkshire dialect speech the COLDWELL name is pronounced with a range of small differences and can sound like “Cow-dell” through to “Cowd-well”. Many of the occasional mis-spellings of the Coldwell surname probably arise from different interpretations of the dialect speech as well as from the variability of spelling. Examples have even been seen in documents where children are named Couldwell whilst their parents are named Coldwell!
Other rare mis-spelt surnames (and possible variants) include Colwell, Colwill, Caudwell, Cauldwell, Caldwall, Calwell, Colwall, Caldwel, Caldwells, Callwell, Calwill, Caulwell, Coldwells, Collwell, Cowgill and Cowlwell.
Some of the rare mis-spelt Coldwell surnames (e.g. CAULDWELL, COWGILL) are by chance also quite separate common family surnames with a different origin and a different progenitor. Care must be taken not to confuse these surnames. Such surnames are not dealt with in this website.
Note that the name CALDWELL is probably not a variant of Coldwell but a separate name originating in Scotland. Rarely the Caldwell spelling is found for a known Coldwell family member.
One of the objectives of the Coldwell/Couldwell DNA project is to confirm the above theories.