Short answer “Kadhoḍ/kathol” means dried pulses/beans (moong, chana, vaal, etc.). Many Jain families prefer them on tithis (like Aatham and Chaudas) because tithi-diet is kept very simple and ahimsak, and greens are commonly avoided on these days. Cooked, unsprouted pulses are considered safer (less chance of harming tiny life-forms) than leafy greens or fermented items, so kathol becomes the natural, allowed sabzi for tithis.

A little more detail

• Ahimsa focus: On selected tithis, Jains tighten food-discipline to reduce even subtle himsa. Greens (saag/hari bhaji) are often avoided; some also avoid curd/fermentation. Dry, stored pulses used without sprouting and cooked plainly involve comparatively fewer jiva-hatti, so they are preferred.
• Saṃyam (restraint): Tithis are meant for extra tapa, pratikraman, and simplicity. A plain meal like rotli-rice, dal/kadhi, and a simple kathol preparation supports that.
• Tradition differences:

- Shvetāmbara: Common practice is to avoid greens on Aatham and Chaudas; many households also keep a “5-tithi” maryādā. What is allowed (kathol, certain non-green sabzi, no-ferments) follows local sangh guidance. - Digambara: Similar restraint on specific tithis; exact lists (greens, curd, etc.) vary by ācārya-maryādā.

• Important notes:

- Unsprouted pulses are used. Sprouting makes “bahu-bīja/bahu-prāṇi” concerns higher, so sprouts are generally avoided—especially in Paryushan/Chaturmās. - Follow your local guru/saṅgh’s maryādā for the exact items permitted on tithis.

For a simple overview of tithis and stricter diet on such days, see: For what’s typically allowed in festival-time/simple diets (similar logic applies on tithis):