The word 'stickleback' is a transparent English compound. The first element, 'stickle', descends from Old English 'sticel', meaning a prickle or goad, itself from the Proto-Germanic root stik-, meaning "to prick," which is also the source of the verb 'stick'. The second element, 'back', is the common English word for the rear part of the body, from Old English 'bæc'. The name thus literally means "prickle-back," a perfectly logical description of the small fish's most distinctive defensive characteristic: the row of sharp, isolated spines along its dorsal ridge. This compound formation follows a classic Germanic pattern of creating descriptive names for animals based on their physical traits.

Structure: stickle (prickle) + back (body part) stickle: From Middle English 'stikel' (a prickle, sting), related to Old English 'sticel' (a sting, goad). It functions as the descriptive element denoting the fish's spiny feature. back: From Old English 'bæc'. It functions as the nominal element specifying the location of the spines.