No probably the two surnames have nothing to do. Saint Tammaro is a local Saint of CAMPANIA the region of NAPLES. BELTRAME is a first name coming from old German (through the French Bertrand). Saint Tammaro was a priest coming from AFRICA. According to Emidio de FELICE (Dizionario Dei Nomi Italiani) the origin of the first name TAMMARO is obscure. However the ethimology you explain could be a possibility. Two things are sure: The surname Tammaro comes from an old first name (now rarely used) The origin of Tammaro is not germanic like Beltramo or Bertrand.