She just mentioned "negative rates" in a live meeting. They're definitely preparing the public for this thing whether or not they actually decide to use it. Here is what she said:
Yellen said she wouldn’t rule out using negative interest rates to help stimulate the economy in the event that another serious downturn occurs before the central bank can lift rates away from zero.
"I don’t at the moment see a need for negative interest rates,” she said. "If circumstances were to change” she added, "potentially anything, including negative interest rates, would be on the table."
Yellen Signals Solid Economy Would Spur December Rate Hike - Bloomberg Business
Economy is going soft. So either its QE, Negative Rates or Something Else.