According to this Wikipedia article:
It can use nearly all of the energy in a single-cell electric battery, even far below the voltage where other circuits consider the battery fully discharged (or "dead"); hence the name, which suggests the notion that the circuit is stealing energy or "joules" from the source. The term is a pun.
Why is it that having multiple batteries in series would not work?
What would happen if the battery was full? (I would assume the device would not oscillate, therefore doing nothing until it was low enough to trip the transistor?)