The word ‘earpiece’ is obviously a joining of the words ‘ear’ and ‘piece’, the term was probably originally coined for eyeglasses at some point in the 18th century, but it also applies to things like old style phone receivers and doctor’s stethoscopes.
British optician Edward Scarlett is thought to have developed the first eyeglass earpieces sometime before 1727. However, this invention didn’t catch on until the early 19th century, so it is probable that the word ‘earpiece’ fell into popular use around that time.
For comparison, American inventor Nathaniel Baldwin built the first radio headphone set in 1919, almost a hundred years later. The basics of earpiece design have existed since that time, so the word ‘earpiece’ was almost certainly used at that point, although it would not have denoted the same device that we now think of today.
Bluetooth headsets, colloquially referred to as ‘earpieces’, were first made commercially available in the early 2000’s and since that time, the term has proliferated. By and large, in the 2010’s, the word ‘earpiece’ tends to refer less to headphones and earphones (although it is still technically accurate terminology) and increasingly solely denotes Bluetooth headsets.
As for the word itself, the word ‘ear’ is actually a derivation of the old English word ēare. It is derived from the same root word as the Norse word eyra and is also cognate with the German word ohr and the Latin auris.
The word ‘piece’ has been in use as far back as the 11th Century AD and comes from the Old French word pece (which is itself of ancient Gaulish origin). It probably also has linguistic ties to the ancient Welsh word peth (meaning ‘thing’).
In the future, it is likely that the word ‘earpiece’ will continue to refer to wearable technology until such time as the word exclusively denotes a wearable device. However, this is purely conjecture on our part.
The other uses for the word will likely remain standard English that simply isn’t used on a daily basis. An example of this would be words like ‘Sellotape’, ‘Tannoy’ and ‘Hoover’, all of which are brand names that do not denote the actual object in question. Correctly, a Hoover is a vacuum cleaner, a Tannoy is a public address system and Sellotape is sticky back plastic. However, almost nobody uses those terms anymore in a casual setting (Alan Partridge and the odd Blue Peter Presenter notwithstanding).