Origins
The word 'mist' is one of the oldest atmospheric terms in English, descending from Old English 'mist,' which meant both thin fog and darkness or dimness more generally. The Old English form comes from Proto-Germanic *mihstaz, with cognates in Dutch 'mist' (fog, mist) and Old Norse 'mistr' (mist, darkness). The PIE root is *h₃meyǵh-, meaning 'to cloud,' 'to make mist,' or 'to drizzle' — a root connected to the concept of fine moisture in the atmosphere.
The etymological family of 'mist' reveals a striking and somewhat indelicate semantic network. The PIE root *h₃meyǵh- appears to have originally referred to any fine spray or moisture, including urination. Sanskrit 'mehati' (to urinate, to make water) comes from the same root, as does Latin 'mingere' (to urinate) — source of the medical term 'micturition.' The connection is that mist, drizzle, and urination all involve fine sprays of liquid. German 'Mist' (dung, manure) represents a further semantic drift along this chain: fine spray → urine → animal waste. The divergence between English 'mist' (atmospheric moisture) and German 'Mist' (manure) is one of the most dramatic examples of semantic shift between closely related languages — the words are genuine cognates from the same Proto-Germanic source, but their meanings could hardly be more different.
In English, 'mist' predates 'fog' by about 800 years. Before 'fog' appeared in the sixteenth century, 'mist' was the primary word for all forms of low-visibility atmospheric moisture. Even after 'fog' arrived, the two words coexist with an imprecise distinction: meteorologically, 'fog' reduces visibility below 1 kilometer, while 'mist' reduces it to between 1 and 2 kilometers. In common usage, however, the distinction is more aesthetic than precise — 'mist' suggests something lighter, more romantic, and more ethereal than 'fog.'
Latin Roots
This aesthetic distinction has made 'mist' the preferred word in literary and poetic contexts. Mist connotes mystery, enchantment, and the boundary between the seen and unseen. In Arthurian legend, the Isle of Avalon is perpetually shrouded in mist. In J.R.R. Tolkien's 'The Lord of the Rings,' the Misty Mountains (Hithaeglir) form the great barrier between the Shire and Mordor. In Japanese culture, mist (kasumi in spring, kiri in autumn) is a standard seasonal element in haiku and classical poetry, representing the transience and beauty of the natural world.
The compound 'misty-eyed' means tearful or sentimental. 'Mists of time' refers to the obscurity of the distant past. 'Misty' as a personal name was popularized by the 1954 song 'Misty' by Erroll Garner (lyrics added by Johnny Burke in 1959), which became a jazz standard.
The distinction between mist, fog, haze, and smog is worth noting. Mist and fog are composed of water droplets. Haze consists of fine particles — dust, smoke, salt crystals — that scatter light and reduce visibility without necessarily involving water. Smog (smoke + fog) originally referred specifically to the mixture of coal smoke and natural fog that plagued industrial cities, but now also describes photochemical smog produced by vehicle emissions reacting with sunlight.
Legacy
In maritime navigation, mist and fog have always been distinguished by their practical impact on visibility. The International Visibility Code classifies atmospheric obscurity on a scale from 0 (dense fog, visibility under 50 meters) to 9 (excellent visibility, over 50 kilometers). Mist occupies the lighter end of this scale — a navigational inconvenience rather than a hazard.