The Spanish word 'binocular' comes from the French word 'binoculaire', which was formed by combining two Latin elements: 'bini' meaning 'pair' or 'two together', and 'oculus' meaning 'eye'. The French term 'oculaire' (relating to the eye) was derived from Latin 'oculus' and then combined with 'bini' to create 'binoculaire', literally meaning 'relating to both eyes'. This word then passed into Spanish as 'binocular'.

Some related Spanish words include 'ojo' (eye), which comes from the same Latin root 'oculus', and 'ocular' (relating to the eye). These connections can help you remember that 'binocular' has to do with both eyes.

The English word 'binocular' is a direct cognate of the Spanish word, sharing the same Latin origins. Other related English words include 'ocular' (relating to the eye), 'oculist' (eye doctor), and 'monocle' (a single eyeglass), all of which derive from Latin 'oculus'. The 'bi-' prefix appears in many English words meaning 'two' or 'twice', such as 'bicycle' and 'bilateral'.