Relieves  headache
Muchenyo widely recognized term for a specific herb. It's possible it refers to a local or colloquial name for a plant used in traditional medicine in Zimbabwe, or it could be a misspelling. The search results indicate that "muchecheni" (Shona) or "umphafa" (Ndebele) refers to the buffalo thorn (Ziziphus mucronata), which is known for its medicinal properties. It's also possible that "muchenyo" is a misspelling of "mugwort" (Artemisia vulgaris), a common herb used in traditional medicine in other parts of the world according to Wikipedia. 
To clarify, here's a breakdown of the possibilities:
1. Buffalo Thorn (Muchecheni/Umphafa):
Scientific Name: Ziziphus mucronata.
Traditional Uses: Used for treating stomach disorders,headache tuberculosis, and boosting immunity.
Availability: Grows throughout Zimbabwe. 
2. Mugwort (Artemisia vulgaris):
Traditional Uses: Used in various traditional medicine systems for different purposes, including digestive issues, menstrual problems, and as an aid for conception according to Wikipedia.
Other Names: Common mugwort, artemisia. 
3. Other Possible Herbs:
Sanjeevani Booti: A medicinal herb from the Himalayas, used traditionally for heatstroke, dysuria, irregular menstruation, and jaundice according to Nadi Tarangini. 
Tansy: Used for intestinal worms, rheumatism, and digestive problems according to Wikipedia. 
Chromolaena odorata: A rapidly growing herb with medicinal properties. 
How to use it
For headache you can use it as snuf
For other diseases  you can mix it with warm water  and drink