|Kundala means coiled, hence Kundalini what is coiled|
Its own form is like a coiled serpent. The TantrarAja says, "The shining [tejas] vital energy [jivasakti], which is the manifestation of life [prAna], is called Kundalini, which resides in the centre of the flames of fire of MulAdhAra. She is sleeping like a serpent, having three [an half ]coils, radiant, she is ever hissing in the centre of SusumnA where she resides, in the head of mAyA. When a man after closing his ears does not hear this sound he is near to death." The YogavAsistha in the story of CUdAla says, "Recognise Kundalini in your Self, which is the very life of the mind which is also called Puryastaka, like the scent in the flower." The Devi Pr. explains that, "She is called Kundalini because she has the SrngAtaka form" [triangle form, and the three angles are icchA, jNAna and kriyA [ vide Yoginihrdaya, I. 51 comm]
Or, the vAghavabija is known as KundalinI.