The word 'spiky' is a straightforward English derivation from the noun 'spike'. The root 'spike' itself has a robust Germanic lineage, traceable through Middle English to the Old Norse spīkr, meaning a nail or spike, a tool defined by its sharp, penetrating point. The adjectival suffix '-y', of Old English origin, is appended to indicate the quality of being full of or resembling spikes. This literal combination evolved naturally to describe not only physical objects like plants or hair but also, metaphorically, human behavior that is sharply defensive, prickly, or prone to pointed confrontation, perfectly mirroring the physical attribute's effect.

Structure: spik(e) (sharp point) + y (adjective-forming suffix) - spik(e): A variant of 'spike', from Middle English, likely from Old Norse spīkr (nail, spike). Its functional role is the core root conveying the concept of a sharp point. - y: A productive English suffix from Old English -iġ, used to form adjectives meaning "characterized by" or "full of." Its role is to convert the noun into a descriptive adjective.