'extraterrestriality' originates from Latin-derived elements: the prefix 'extra-' (Latin 'extra' meaning 'outside, beyond') and the adjective 'terrestrial' (from Latin 'terra' meaning 'earth'), combined with the nominalizing suffix '-ity'.

'extraterrestriality' developed by attaching the abstract noun suffix '-ity' to the modern English adjective 'extraterrestrial' (itself formed from 'extra-' + 'terrestrial'), producing an English abstract noun that expresses the state or quality of being beyond the earth.

Initially the roots conveyed simply 'outside' + 'of the earth'; over time the compound and nominalized forms have been used to denote specifically the state or quality of being of extraterrestrial origin or nature, as in current scientific and speculative contexts.