Your S.C.A. name is the name you'll use at S.C.A. activities. The S.C.A. models itself on Europe as it was before 1600 A.D.,
so the name you pick should be one that might actually have been used then. However, you shouldn't adopt the name of a real
historical person; the S.C.A. doesn't reenact the events of those times, so historical figures don't belong at S.C.A. events.
Your SCA name should also be different from your legal name, to reflect the difference between your modern and S.C.A. identities...
Your heraldic device (informally, your "coat of arms") is essentially your personal "logo," and identifies you the way a
company's logo identifies the company. On a banner, it tells everyone you're at an event. On a shield, it tells who's on the
field fighting. On tableware, it tells whose place it's at. On clothing, it tells who's in the clothing.