Which is the correct spelling? Chile pepper - Chili pepper - Chilli pepper
Capsicum annuum (common varieties such as bell peppers, paprika, jalapeños, and the chiltepin)
Capsicum frutescens (includes cayenne and tabasco peppers)
Capsicum chinense (includes the hottest peppers such as habaneros and Scotch bonnets)
Capsicum pubescens (includes the South American rocoto peppers)
Capsicum baccatum (includes the South American aji peppers)
Technically, chili peppers are a fruit. Once dried, they are considered a spice.
Chile pepper, chili pepper, chilli pepper - which is the correct spelling?
Each of the three spellings is recognized by different dictionaries as being correct. The Oxford English Dictionary shows "Chilli" as the primary spelling while citing both Chile and Chili as variant spellings. Websters gives equal weight to both chili and chilli but chile is not included. Chile is most frequently used by Americans though chili is also quite common, though this word also refers to the Southwestern bean dish (chili con carne, vegetarian chili). Google searches of the words combined with "pepper" shows "chilli" in the lead. Which is correct? That's up to you - just don't call them chilly.
More Confusion - Why pepper?
Columbus was looking for a more direct route to Asian countries that produced valuable spices like black pepper, but he bumped into the Americas along the way. When Columbus and crew landed in the New World, they stuck an erroneous and confusing moniker on the native chiles. He named them "peppers" because they spiced up food just the way black pepper did. We credit Columbus for being politically astute choosing "pepper" as a name considering his Spanish sponsors were looking for a spice route. It took about two centuries for botanists to figure out that chile peppers belong to the genus Capsicum, a totally different botanical family than black peppers.