Split step, split drop, prep jump, "step one" by LJB, pre load jump
These are all terms for the same thing - the "loading" of the legs prior to explosive movement. Some people achieve it in different ways, but it usually involves the widening of the distance between the feet (hence use of the word "split") and the loading of the legs by bending slightly at the knees (hence us of the word "drop"). Many people achieve this naturally by doing a little "hop" in the air (hence use of the word "jump"), but some just bend the knees and widen the base, particularly when short on time.
I wouldn't say "split drop" is particularly common. I have only ever really heard it referred to as split step by coaches, but I have heard all the variations at some point.