Origins
The word 'spice' has a remarkably intellectual origin for something so sensory. It descends from Latin 'speciēs,' a noun meaning 'appearance,' 'form,' 'kind,' or 'sort' — the same word that gave English 'species' in its biological sense. The two words are doublets: the same Latin source borrowed into English twice through different channels, producing two words with divergent meanings but identical ancestry.
Latin 'speciēs' derives from the verb 'specere' (to look at, to behold), from PIE *speḱ- (to observe). This root is one of the most productive in the Latin-to-English pipeline: 'spectacle,' 'spectrum,' 'speculate,' 'specimen,' 'special,' 'specific,' 'aspect,' 'inspect,' 'respect,' 'prospect,' 'suspect,' 'expect,' 'conspicuous,' 'despise,' 'spy,' and 'scope' (through Greek 'skopein,' from the same PIE root) all trace back to *speḱ-. The fundamental concept is seeing or observing, and its descendants cover everything from philosophy to optics to commerce.
The semantic journey from 'appearance' to 'spice' is a case study in how commercial language evolves. In Classical Latin, 'speciēs' meant 'the look of a thing,' 'a kind or sort,' 'a visible form.' In Late Latin (roughly 3rd–6th centuries CE), it developed a commercial sense: 'goods,' 'wares,' 'merchandise' — things sorted by kind. The plural 'speciēs' in this commercial sense came to refer specifically to the most valuable and exotic trade goods: the aromatic substances — pepper, cinnamon, cloves, nutmeg, ginger — imported from Asia at enormous expense. These were 'the goods' par excellence, the most noteworthy 'kinds' (speciēs) of merchandise.
French Influence
Old French inherited this narrowed meaning as 'espice' (modern French 'épice'), and English borrowed it around 1200 as 'spice.' The word arrived in English already specialized to mean aromatic flavourings, with no trace of its original sense of 'appearance' or 'kind.' Meanwhile, the learned Latin form 'speciēs' was borrowed directly into English in the sixteenth century in its original sense of 'kind' or 'sort,' and was eventually adopted by Linnaeus in the eighteenth century as the technical term for a biological species.
The economic importance of spices in the medieval and early modern world can scarcely be overstated. Pepper, cinnamon, cloves, and nutmeg were among the most valuable commodities in existence, worth more by weight than gold. The spice trade drove the Age of Exploration: Columbus sailed west seeking a route to the Spice Islands; Vasco da Gama rounded the Cape of Good Hope for the same reason; the Dutch East India Company was founded to control the spice trade. The fact that the Latin word for 'kind' or 'sort' narrowed to mean specifically these substances is a linguistic reflects their economic dominance.
The word 'spice' has developed metaphorical senses in English: 'the spice of life' (variety), 'to spice up' (to make more interesting), and 'spicy' (racy, provocative). These metaphors all exploit the sensory intensity of spices — their power to transform bland food into something stimulating — as a figure for any quality that adds interest or excitement.