Namu Daishi Henjo Kongo ( 南 無 大師 遍照 金剛) is an inscription found on many of the equipment of the Shikoku Pilgrim. It is a Shingon Buddhist sutra in honor of its founder Kukai (or Kobo Daishi).
Let’s try to explain the meaning:
南無 Namu is a greeting that expresses respect as Ave in Latin or Amen in Catholicism, its origin is Sanskrit.
大師 Daishi is the name (posthumous title) given to Kukai and means grand master in the sense of one who has reached knowledge and sharing it.
遍照 Henjo marks enlightenment in the Buddhist sense of the term, it’s mean a human being who has reached enlightenment.
金剛 Kongo can be translated as diamond but in its Sanskrit sense, it is something precious and imperishable. It is the Buddhist symbol of the indestructible truth.
Miyata Taisen, Shikoku Pilgrimage and Shingon Buddhist Specialist, suggest this translation
Homage to the Savior [Kōbō] Daishi, the Illuminating and Imperishable One.