Board Thread:Questions and Answers/@comment-75.162.18.243-20200222233912/@comment-35248429-20200224071833

It's a 27 hit combo for the dual blades skill. It's the attack that Kirito uses against Kayaba at the end of their second duel.

''I changed my attack pattern and activated «The Eclipse», the highest level Dual Blades skill. Like the tips of an enveloping corona, my swords sent twenty-seven consecutive attacks towards Kayaba—''

You can probably see by the description why it has it's name.