'uninuclear' originates from Latin-derived elements: the prefix 'uni-' (from Latin 'unus') meaning 'one' and 'nuclear' from Latin 'nucleus' meaning 'kernel' or 'core'.

'uninuclear' was formed in modern scientific English by combining the Latin-derived combining form 'uni-' with the adjective 'nuclear' (from Latin 'nucleus'); the compound arose through Neo-Latin and 19th–20th century scientific usage into the current English form 'uninuclear'.

Initially it literally meant 'having one nucleus' as a direct compound of 'uni-' + 'nuclear', and this literal scientific meaning has remained stable.