begin, be damaged, break, fall
剏 centers on the idea of initiating something, but the given meanings also include breaking, being damaged, and falling. These meanings do not share one clear conceptual center; the character may have been used for both starting and breaking, possibly through the idea of cutting or striking with a blade.
剏 combines 并 and 刃 (blade). The exact historical development is uncertain; it may have originally represented cutting or striking with a blade, which could relate to both beginning (cutting into something new) and breaking.
The left side 并 looks like two lines joined, and the right side 刃 is a blade. Imagine a blade cutting into a joined pair, starting a split that can also break or damage them.
For ソウ, imagine a saw (ソウ) blade cutting into the joined pieces, beginning the work: saw -> ソウ.