The Scintillant Hummingbird (Selasphorus scintilla Gould) is among the smallest of hummingbirds, and is the smallest within its range of the Pacific slope of Costa Rica and western Panama. Despite its diminutive size, it is a striking bird that is difficult to overlook, or to forget once seen. The wing trill of the adult male can be heard at a distance, and the male’s blazing orange gorget is spectacular against its rufous plumage. It appears to be most closely allied with Allen's (S. sasin) and Rufous (S. rufus) hummingbirds of North America, as well as Glow-throated Hummingbird (S. ardens) of Panama. Scintillant is allopatric to all of these species, whereas it is sympatric with Volcano Hummingbird, S. flammula, a species with which Scintillant sometimes is confused.

Swainson (1830) named the genus Selasphorus, which means “Light-bearing” (Coues 1882), with Rufous Hummingbird as the type. With a virtually identical gorget, the same description is apt for the Scintillant. Scintillant was described by Gould (1850), in which he noted its small size and beauty. Scintilla means “a spark” in Latin (Lewis and Short 1879), thus Selasphorus scintilla means a “light-bearing spark”.

https://birdsoftheworld.org/bow/species/scihum1/cur/introduction