'non-galactic' originates from English, formed by the prefix 'non-' and the adjective 'galactic', where 'non-' meant 'not' (from Latin 'non') and 'galactic' derives from 'galaxy'.

'galactic' comes from Greek 'galaxias' (from 'gala' meaning 'milk'), passed into Latin and later into English as 'galaxy/galactic'; the prefix 'non-' was adopted from Latin 'non' and became a productive English prefix forming negations (e.g. non- + adjective).

Initially 'galactic' referred specifically to the Milky Way (the 'milky' circle) and later to galaxies in general; 'non-galactic' has been used to denote things not belonging to or not associated with any galaxy.