What was the clarinet originally used for?

Answer 1

The Chalumeaux. It was very popular shortly after its invention in the late 17th century, as it sounded like nothing else availiable at the time. Though the name now belongs to the bass register of the Clarinet family, there are plenty of companies online that make very good replicas of the original instrument.

Answer 2

The earliest writing for clarinet in late baroque music has it only doubling other instruments or when it was on its own it was in pairs and treated like a pair of rather less attractive oboes.

Answer 3

The oldest name for the clarinet is Chalemeau. It is nothing like the modern day Bb Clarinet other than it's straight and requires a reed.

Answer 4

Jazz musicians often referred to it as a 'stick'

People commonly call it 'horn', but that is also said for other woodwind/brass instruments. So, I guess it can work either way.