where did ``xxx" quotes come from?

Ive seen the quoting style of using 2 backticks (``) in front with regular double quotes on the end of something being quoted. Im assuming this is from K&R, but does anyone know where that originates from and if there is any practical reason for it?

>>15
awesome and cool way to quote
Suuuuure, let's all just destroy the English language by using grave as a quote character, when it has no functional purpose.