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?

>>12
No. You are the jerkface, spreading lies and subterfuge. There are the awesome and cool way to quote. Sussman agreed, don't bother him about it.

>>14
Agreed.