Self-component — also
月's own indexing radical (Kangxi #74). The oracle-bone form depicted a crescent moon with a dot inside, the curve and inner mark surviving in the modern shape as the outer hook plus the two horizontals. Borrowed early on for 'month' (one lunar cycle). When
月 appears on the LEFT of other characters it is usually the flesh radical ⺼, a separate origin — this is the moon
月.
