Electroluminescent wire
en.wikipedia.org/wiki/Electroluminescent_wire
Article
Electroluminescent wire
Capacitive light source in the form of a wire
From the page
Saved with the link. Notes from 2007 to 2016 are mostly the page's own words, so this is probably an excerpt.
Electroluminescent wire (often abbreviated to EL wire) is a thin copper wire coated in a phosphor which glows when an alternating current is applied to it.