From Wiktionary, the free dictionary
Sino-Vietnamese word from 修行.
tu hành
- (Buddhism) to undergo ascetic training
Copy from 18th century, Urtext probably from 12th or 15th century, Phật thuyết đại báo phụ mẫu ân trọng kinh (佛說大報父母恩重經):迈虽𪜀弟子哿蚤多修行虽浪它娄㝵咍事某渚曠- Although you are my eldest student, who has trained for a long time, your knowledge is not yet wide.