Youtube username pops up when people enter my gmail address

[sdms96825]

I'm not sure what is going on but all of a sudden when someone enters my email address or name in their "To:" line on their gmail, my youtube username pops up in addition to my gmail name. I remember using that username on youtube to enter a single comment (not profane!) to some misguided economist. How can I get rid of this? Even when I start to type in my name in Thunderbird, it shows my youtube username. Very frustrating. Thanks.