An Etymological Dictionary of Astronomy and Astrophysics

1. A sudden blaze or burst of fire or light.
   

2. → solar flare.

Etymology (EN): From v. flare “to spread out,” said of hair, a ship’s sides, etc., of unknown origin.

Etymology (PE): Âlâv, “blaze, fire,” variants alow, Borujerdi elew “fire,” Garkuyeyi alôv “flame,” Hamadâni elow “flame,” Lori alô “flame,” Tabari aluk “flame, spark,” Torbat-Heydariyeyi alow “flame;”
cf. Gk. aithos “fire,” aitho “to kindle;” Skt. edh- “to set alight, kindle,” édha-, édhas- “firewood;” Av. aēsma- “firewood;” Mod.Pers. hizom, himé “firewood;” PIE base *aidh- “to burn,” *aidhos- “fire.”