the.com/electroscope

means An early instrument that detects and shows the presence of electric charge by using the repulsion between two thin, charged leaves (often gold foil) that spread apart as charge increases.

from Built from Greek roots: 'electro-' traces back to 'elektron,' the Greek word for amber — because rubbing amber was one of the first ways humans ever produced static electricity — fused with '-scope,' from 'skopein,' meaning 'to look at or examine.' So the word is literally 'amber-looker,' a name coined as scientists in the 1700s–1800s built devices to make the invisible force of static charge visible through the splaying of delicate leaves.