The Greek noun gerōn (γέρων) means an old man or elder — one advanced in years. It appears once in the New Testament (John 3:4), where Nicodemus, puzzled by Jesus's teaching, asks how a man can be born again when he is 'old' (gerōn). The word captures the impossibility of physical rebirth from Nicodemus's literal mindset.
Nicodemus's question — 'How can a man be born when he is gerōn (old)?' — is not mere misunderstanding but represents all of humanity's inability to grasp spiritual birth. Physical age is irrelevant to the new birth; what matters is the sovereign work of the Spirit. This exchange gives us Jesus's most complete teaching on regeneration: it is not physical, not self-generated, but from above (anōthen), by water and Spirit. Even the oldest, most established religious teacher must be born again.