How did "barbershop singing" get its name?

How did “barbershop singing” get its name? Was there a time in America when barbers and/or their customers would routinely break out in acapella four-part harmony? Right there in the shop, with the hair all over the floor and everything?

A brief history of barbershop

Acording to this page, barshop music stemmed from African-American tradition, and came about because, it seems, barbering was considered the province of that sector of society, as well as that of immigrants, as a low-status job.

The advent of the image we see today of barbershop quartets is relatively recent.

Two excellent links that answered questions I had never thought to ask. Thanks, Otto and Ice Wolf!