Athara means
Sri Caitanya-caritamrta
CC Madhya-lila
Āṭhāra means eighteen.
CC Madhya 5.147, Translation and Purport: Thus walking and walking, the Lord eventually arrived at the place known as Āṭhāranālā. Arriving there, He expressed His external consciousness, speaking to Śrī Nityānanda Prabhu.
At the entrance to Jagannātha Purī is a bridge with eighteen arches called Āṭhāranālā. (Āṭhāra means eighteen.)