This unusual name is a transposed spelling either from the Irish O'Brosnan which seems the most likely as it is also spelt Bresnane in Co. Kerry, or from the French Bresnard, a name recorded heraldically from Brittany. As it happens the Irish name may itself derive from the French, the earliest Irish recording being 14th Century - some two hundred years after the original 1169 Anglo-French invasion of Ireland. The first O'Brosnans were recorded as being food-producers or 'bretaghs' in the Gaelic. The first recorded spelling of the family name is shown to be that of O'Brosnachain. which was dated 1333 Clonmel, Tipperary. during the reign of King Edward 111 The Father of the Navy, 1327 - 1377. Surnames became necessary when governments introduced personal taxation. In England this was known as Poll Tax. Throughout the centuries, surnames in every country have continued to "develop" often leading to astonishing variants of the original spelling.