The Avestan word amərətatāt-
Word amərətatāt-
Meaning immortality

Other words that might be of interest
hunu-š ‘son’, pairikā ‘witch’, ahu- ‘life, existence’, āiiu- ‘age, life’, nar- ‘man’, nāirī ‘woman’, mašiia- ‘mortal, man’, vīra- ‘man’, napāt- ‘grandson’