'bluish-gray' originates from modern English, specifically the combination of 'bluish' and 'gray', where 'bluish' is formed from 'blue' + suffix '-ish' meaning 'somewhat' and 'gray' denotes the color gray.

'bluish' developed from 'blue' plus the adjectival suffix '-ish' (with 'blue' tracing back through Middle English 'bleu' to Old English and Proto-Germanic roots), and 'gray' comes from Old English 'grǣg' (from Proto-Germanic *grēwaz); the compound 'bluish-gray' was formed in modern English to describe an intermediate color.

Initially, the components meant 'somewhat blue' and 'gray' respectively; combined they retained a descriptive meaning for a color between blue and gray and evolved into the modern usage meaning 'somewhat blue-gray'.