A few relevant points made by Govindarajan in this 1985 paper[1]:
> Chilli or Chili, a name now commonly used in Asia and Africa, is said to have come from the Nahautl dialect of Mexico and Central America.
> The U.S. Government Standard divided Capsicum into types corresponding to commercial types; paprika, red pepper, ground and crushed. The term "chilli" is not generally used in the U.S., but is used in Britain, India, Africa, and the countries in the East.
> The British Standard Specifications, however, differentiate between chillies and capsicum, obviously based on the degree of pungency. It gives no values but describes "chillies" as pungent small fruits of certain forms of the species C. frutescens L. and describes Capsicum as of varied sizes, generally big, of the species, C. annuum L.