'cardinalfish' is a compound of English 'cardinal' and 'fish'. 'Cardinal' originates from Late Latin 'cardinalis' (from Latin 'cardo' meaning 'hinge' or 'principal'), and 'fish' originates from Old English 'fisc'. The compound name likely refers to the bright red or conspicuous coloration (associating with the color/name 'cardinal') of some species.

'cardinal' came into English via Late Latin 'cardinalis' → Old French/Medieval Latin forms → Middle English 'cardinal', while 'fish' came from Old English 'fisc' → Middle English 'fish'. The compound 'cardinalfish' developed in modern English as a name for members of the Apogonidae family (used in zoological and common speech).

Originally 'cardinal' primarily meant 'principal' or 'chief' (from Latin), but its association with the red color of the cardinal bird led to 'cardinal' being used to describe a red hue; in 'cardinalfish' the element 'cardinal' refers to the fish's conspicuous (often reddish) coloration rather than the original 'principal' sense.