The name Katharine is a girl's name of Greek origin meaning "pure". Katharine and is often added to lists like Unique Vintage Names for Girls and discussed in our forums with posts like "Change Two Letters".
From the experts:
This is the spelling that old-time film star Katharine Hepburn used, and it's still favored by fans wanting to reference her classic strength and beauty. But in general, it's losing ground to Katherine and even Ms. Hepburn's own favorite short form, Kate.