there were/are Mahons in Coxhoe/Cornforth so these may be your family?
Name: Nicholas Mahon
Spouse: Annie
Birth: abt 1858 - Coschoe, Durham, England
Residence: 1901 - Cornforth Lane, Cornforth, Durham, England
also
Name: Nicholas S Mahon
Spouse: Eliz Jane
Birth: abt 1860 - Cornporth, Durham, England
Residence: 1901 - Ferry Hill, Ferry Hill, Durham, England
Name: Robert Mahon
Spouse: Mary Ann
Birth: abt 1837 - Coxhoe, Durham, England
Residence: 1871 - Coxhoe, Coxhoe, Durham, England
amongst others