The word "Thirumanjanam" means Holy bath. Aani Thirumanjanam (Tamil month spanning June-July) is a special day (Uthram Nakshtram) when an Abhishekam is performed for Lord Nataraja. It is believed that Lord Nataraja gives darshan to his devotees in the months Aani and Margazhi. The Lord's form demonstrates his five-fold functions: creation, preservation, destruction, concealment and salvation.
The rattle (udukkai) in his right hand represents creation; his raised right arm with the open palm (abhaya hastam) protection; his left hand holding fire destruction; his firmly placed foot concealment; and his other, slightly lifted, leg salvation. Lord Nataraja is given six abhishekams in a year. Earth takes 365 days to complete one full circle around the sun.
That duration of Tamil months is divided into six seasons - Marghazhi-Thai: early winter; Maasi-Panguni: late winter; Chittirai-Vaikasi: early summer; Aani-Aadi: high summer; Avani-Purattasi: autumn; Aippasi-Karthikai: rainy season. This six-season year of humans is said to be one day for the immortals. A day has six periods: dawn, morning, noon, afternoon, evening, and night. These are when the six daily poojas (Kaala Pooja) in temples are performed. During each of these six parts, an Abhishekam has been ordained for Lord Nataraja. One of these is Ani Thirumanjanam, the pradosha abhishekam on the evening of the day of Uthiram star in the Tamil month of Aani (June-July).