A Sept is a division of a Clan, though of another family name. They have historically affiliated with the larger clan, and given fealty to the Clan Chief. The variety of surnames within a Scottish clan do not represent separate and definable sub-clans but instead reflect the vagaries of transition of the Gaels into the English naming system as well as marriages, migrations and occupations. The main family itself may therefore have developed a variety of surnames.
Common alternative spellings of the name Fraser are Frasier, Frazier, Frazer, Frasee, Frissell, Frizell. Common Septs of Clan Fraser include Simpson, Bisset, Lovat, Lovet, Loveth, Macimmey, MacKimmie, MacShimes, MacSimon, MacSymon, MacTavish, Oliver, Sim, Sime, Simon, Simpson, Sims, Simson, Syme, Symon. Further information can be found here: https://www.electricscotland.com/webclans/septs.htm