The word originates from a well-known figure in the world of HEMA - Historical European Martial Arts - who was famed as a skilled fencer with sword and buckler, a creative artist and animator, and an informal guru to hundreds.
The word originated in the early days of computing when he first got an email account. His girlfriend said, "I suppose you'll call yourself 'Swordflasher' or something..."
"My God, what a bout. That was incredible! We'll have to call you 'Swordflasher' from now on!"
"Well, Pierce Brosnan was a pretty good Bond - but he was no swordflasher."