I don't know what tahjhad means but it sure sounds like tahajud. Tahajud is the prayer that Muslims pray in the last quarter of the night in Ramadan. Usually, it starts around 3 and ends right before fajr and suhoor time. In some mosques in the US, the Imam, while praying tahajud and everyone is praying behind him, there are people cooking suhoor for the Muslims to eat. Very fun nights, I've been to them and helped out.