In folklore wills-o'-the-wisp are typically attributed as ghosts, fairies, or elemental spirits. Modern science explains the light aspect as natural phenomena such as bioluminescence or chemiluminescence, caused by the oxidation of phosphine (PH3), diphosphane (P2H4) and methane (CH4), produced by organic decay.
Nonoka said she hasn't seen that color before, implying it wasn't a chemical reaction she, who well-versed in science, know of. So it prbly not a natural phenomenonFrom Wikipedia
It is called Natrium in many other languages too.Minor note, but "natrium" is more commonly known in English as "sodium". Natrium is an older term for the element and is the reason why it is abbreviated Na.