Sirname

Fair Helen's sirname, therefore, depends upon the period at which she lived, which it is now impossible to ascertain.

Source: wiktionary

These names were not always used; commonly two, and sometimes only the sirname.

Source: wiktionary

They were in two trunks (made exactly fit for them) that had the first letters of my christian and sirname decyphered upon them with nails; and on the first page of every book was my ordinary motto and name written at length in my own hand.

Source: wiktionary