In Jainism, "Siddhi Tap" is not a widely recognized or traditional term for a specific austerity or penance. Jain scriptures describe various types of penances (tapas), such as Nava Tapa, Varsitap, Ayambil, and others, but "Siddhi Tap" does not appear as a standard practice in the canonical texts.

However, in some Jain communities, especially among lay followers, new forms of tapas or religious practices may be introduced or popularized by revered monks, nuns, or spiritual leaders as means to attain spiritual progress or "siddhi" (spiritual accomplishment). The specific origin or person who started "Siddhi Tap" would depend on the local tradition or community and may not be documented in classical Jain scriptures.

If you have more details about the practice or the context in which you encountered "Siddhi Tap," please provide them, and I can try to give a more specific answer based on Jain teachings.