Y'know

"Can a phrase be repealed? I have in mind Y'know. The prevalence of Y'know is one of the most far-reaching and depressing developments of our time, disfiguring conversation wherever you go. I attend meetings at NBC and elsewhere in which people of high rank and station, with salaries to match, say almost nothing else.
For a while I thought it clever to ask people who were spattering me with Y'knows why, if I knew, they were telling me. After having lunch alone with some regularity, I decided to drop the question. 
Once it takes its grip, Y'know can be hard to throw off. Some people collapse into Y'know after giving up trying to say what they mean. Others scatter it broadside, these, I suspect being embarrassed by a silence of any duration during which they might be suspected of thinking about what they were going to say next.
...there is some reason to believe that [Y'know] began among poor blacks who, because of the various disabilities imposed on them, often did not speak well  and for whom Y'know was a request for assurance they they had been understood. From that sad beginning it spread, among people who wanted to show themselves sympathetic to blacks, and among those who saw it as the latest thing and either could not resist or did not want to be left out.
Those who wanted to show that they were down to earth, and so not above using Y'know, have been particularly influential. They include makers of television commercials who begin the sales pitch with Y'know, and so gain the confidence of the viewer, who realizes at once that the person doing the commercial is down to earth, regular, not stuck-up, and therefore to be trusted." 

Strictly Speaking, Edwin Newman, 1974