Charles Ellson wrote:

In other cases there was an established spelling but as applies in
this someone came along later and recorded/copied it incorrectly.
Rum/Rhum
Hannover/Hanover
Hazelton/Hazleton (Pennsylvania - allegedly misspelled in the
incorporation documents in 1857 and "it's too late to change it now")

Surely Hannover/Hanover is not a misspelling, but simply the English
version - cf Wien/Vienna and countless others. Admittedly nowadays in
many cases the "native" version is normally used - Brits used to refer
to Coblence, Mayence, Brunswick, Frankfort and the like.

Peter Beale