There are a couple of reasons I used the term "splicing" for Dark Splicing. I was originally thinking about splicing rope. You take two lengths of rope, or a single rope that has been cut, and you unbraid the rope and then braid it back together connecting the two ends. With magic you are taking the building blocks of existence and taking them appart and braiding part it back into yourself. It's "dark" because the negative energy part is not braided back in and is left unaccounted for.
The other reason is that the term sounded neat, it's not overused and it's not so technical that it's confusing. Hawking's kind of got the market on fission. Those that figured out I was talking about fission - cool. Those that didn't could just lean on the more medival sounding term Dark Splicing and use it as a new kind of magic.
I hope that clears it up - otherwise I'm going to have to try make something out of nothing.
Mark Charke