Rattlesnake is the way the coil sizzles.
Originally, way back when, the 'rattlesnake effect' was a term coined for the constant 'up and down' voltage application of inefficient and poorly designed boards that couldn't hold a sustained voltage.
Meaning the board, when the the fire button was pressed continuously, applied an irregular amount of voltage in an up and down fashion to the atomizer which made it crackle and pop up and down as voltage was applied like a 'rattlesnake'.
Did that make sense?