'isochromic' originates from Greek, specifically the elements 'isos' and 'chroma', where 'isos' meant 'equal' and 'chroma' meant 'color'.

'isochromic' was formed in Modern/Neo-Latin (via constructions such as 'isochromicus') from Greek roots and was adopted into English with the same compound sense, producing the modern English adjective 'isochromic'.

Initially, the compound literally meant 'equal color'; over time it retained that core sense and came to be used in scientific contexts to describe uniformity of color or identical spectral properties under given conditions.