English

hairspring

From hair + spring.

A compound of hair + spring

Proto-Germanic *hērą

Proto-West Germanic *hār

Old English hǣr

Middle English her ‘a hair’

English hair

Proto-Indo-European *sperǵʰ- ‘to hurry’

…

Proto-Germanic *springaną ‘to burst forth’

Proto-West Germanic *springan ‘to spring’

Old English springan ‘to spring’

Middle English springen

Today it means

noun A spring, made of a coil of fine wire, that is used to regulate the movement of a balance wheel in a watch.

Language periods are conventional ranges, not dates for this word.

Etymograph / hairspring