Delhi boil refers to:
Cutaneous leishmaniasis is the most common form of leishmaniasis affecting humans. 
It is a skin infection caused by a single-celled parasite that is transmitted by the bite of a phlebotomine sandfly. 
This disease is considered to be a zoonosis (an infectious disease that is naturally transmissible from animals to humans), with the exception of Leishmania  tropica. 
Other names are Oriental sore, Tropical sore, Chiclero ulcer, Chiclero's ulcer, Aleppo boil, Delhi Boil or Desert boil.

Ref :https://en.wikipedia.org/wiki/Cutaneous_leishmaniasis
Solar Keratosis
Malignant pustule
L. tropica sore
Venereal ulcer