boil, seethe
茹 centers on cooking something in hot liquid: boiling or seething food, especially vegetables or other plant matter.
茹 combines 艹 (grass/plant) with 如, which likely contributes the sound. The plant component suggests boiling plant matter.
The grass radical 艹 sits above 如, like a bundle of herbs being lowered into a pot to boil.
For ジョ, imagine a chef named Joe boiling a pot of greens: Joe -> ジョ, and the herbs 艹 bubble in the water.
to boil (something in hot water)
to boil; to seethe
parboiling; preparatory boiling
boiling with salt; boiling in salty water (e.g. vegetables)
half-boiled; insufficiently boiled; underdone
boiling
to boil, then discard the liquid (in order to remove astringency)
boiled octopus
to be completely boiled; to be sufficiently boiled
to boil (something) until it is done
boiling time
boiled red prawn, shrimp, lobster, etc. (sometimes used as a New Year decoration)
boiled crab
boiled pork
boiling in an iron pot