Where does “kaṭhina” come from?

kaṭhina (Pali) comes from Sanskrit कठिन, from Sanskrit कठ् — to live in distress.

kaṭhina (Pali): embroidery hoop

Definitions

Step	Language	Word	Meaning
1	Sanskrit	कठिन	difficult; stiff, hard, firm; harsh, cruel,...
2	Sanskrit	कठ्	to live in distress

kaṭhina — Etymology, Origin & Word History | Etymology Explorer