Chinese matrimony vine, tilling public fields, corvee, surname
莇 is a rare kanji with several distinct meanings that do not share one clear conceptual center. It can refer to the Chinese matrimony vine plant, the act of tilling public fields or corvée labor, and is also used as a surname.
The exact historical development of 莇 is uncertain. It combines 艹 (grass) with 助, but the original semantic and phonetic roles are unclear.
The grass top 艹 suggests a plant, and the bottom 助 (help) can be seen as helping with public fields. Picture a vine growing over a field where workers are helping to till the land.
For ジョ, imagine a worker named Joe tilling the public fields under the Chinese matrimony vine: Joe -> ジョ.