Origins
Nostril is one of the more transparent compounds in English — once you know what you are looking at. It comes down to us from Old English nosþyrl, built from two pieces: nosu (nose) and þyrl (hole, perforation, opening). A nostril is, with perfect anatomical literalness, a nose-hole. The Anglo-Saxons had no patience for circumlocution when naming the parts of the body.
The first element, nosu, traces back to Proto-Germanic *nasō, which in turn descends from the Proto-Indo-European root *nas-, meaning nose. This root is among the most stable in the Indo-European family. Latin nasus is a direct cognate, as is Sanskrit nāsā. The nose was one of those features of the human face that speakers across the language family agreed on naming early and naming consistently. From the steppes of Central Asia to the shores of Britain, speakers of languages descended from Proto-Indo-European were reaching for the same ancestral syllable when they needed a word for the organ of smell. In English, nosu evolved steadily through the Old English and Middle English periods, shedding its inflectional ending and arriving at the modern nose without drama. The word has cognates throughout the Germanic branch: Old Norse nǫs, Old High German nasa, Dutch neus, German Nase.
The second element is the one that repays closer attention. Old English þyrl means a hole, perforation, or opening — specifically a hole made by piercing or boring through something. It derives from Proto-Germanic *þurhilą, itself formed on *þurhą, meaning through. The semantic connection is direct: a þyrl is what you have when you go all the way through something. This Proto-Germanic *þurhą is the ancestor of Modern English through, and it connects to a family of words built on the concept of passage, penetration, and traversal. The same root gives us thorough, which originally meant simply going all the way through before it acquired its modern sense of completeness. When you describe someone as a thorough worker, you are, at several removes, invoking the same root that names the hole in your nose.
Proto-Indo-European Roots
The prehistory of þyrl offers a clear demonstration of the consonant shift first systematically described by Jacob Grimm in the second edition of his Deutsche Grammatik in 1822. The Proto-Indo-European root behind through and þyrl is *terh₂-, meaning to cross, to pass through. In Latin, the reflex of this root appears in trans — across, through — and in tres, three (three being the number that crosses to the other side of two). In PIE these words began with t. In Proto-Germanic, by the operation of Grimm's Law, that original *t shifted to *þ — the dental fricative, the sound written th in Modern English. This is why tres in Latin corresponds to three in English, and why trans corresponds to through. The Germanic languages, as a group, applied this systematic shift to the inherited voiceless stops: p moved to f, t moved to þ, and k moved to h. The þ in þyrl and in through is precisely this shifted t. When you say nostril, the -tril ending carries the ghost of an Indo-European t that became Germanic þ and then, in the particular phonological history of the word, shifted back toward a t sound in the cluster.
There is a word closely related to þyrl that has travelled a long distance from its origins: thrill. The Old English verb þyrlian meant to pierce, to bore a hole, to perforate. A þyrl was the hole; þyrlian was the act of making one. In Middle English the verb thirlen persisted in this concrete, physical sense — you could thirl a board by driving a nail through it. Somewhere in the later medieval period the word's meaning began to shift. The physical act of piercing gave way to a metaphorical sense: a sudden, sharp sensation, as if something had pierced through you. By the early modern period, thrill had completed its journey from carpentry to feeling. The word that once described boring a hole now described a wave of excitement or fear that seemed to penetrate the body. Nostril and thrill, then, are etymological cousins. Both descend from the same Old English root þyrl. The nostril is the hole in the nose; the thrill is the sensation of being pierced.
What makes nosþyrl historically significant is not only its etymology but its survival strategy. Latin had its own word for nostril — naris, plural nares — and Latin anatomical vocabulary was the prestige register of medical and scholarly writing throughout the medieval period. The Norman Conquest of 1066 poured a further tide of French and Latin vocabulary into English, particularly in the domains of law, court, cuisine, and medicine. Yet the Anglo-Saxons had built their anatomical vocabulary from native materials, compounding existing words to name the parts of the body. Nosþyrl for nostril. Eardrum for the tympanic membrane. Elbow. Shinbone. Ankle. Wrist. These compounds were direct, functional, and deeply embedded in everyday speech — and they survived because ordinary people kept using them. Nosþyrl survived. The Norman scribes did not replace it with naris. The word simply continued, shedding its Old English inflections, adjusting its spelling — nosethirl (c. 1300), nosethril (c. 1400), nostril (from the early sixteenth century onward) — but preserving the compound structure intact. Chaucer uses nosethirles in the Canterbury Tales. The King James Bible of 1611 has nostrils in Genesis 2:7, where God breathes into Adam's nostrils the breath of life. The nose-hole is still called the nose-hole in English, a thousand years after the last speaker of Old English died.
Cultural Impact
Cross-linguistic comparison shows how unusual the English compound is. German preserves a similar strategy with Nasenloch (nose-hole), a transparent modern compound with the same logic, though the standard medical term in German is Nasenflügel for the wing and Nasenöffnung for the opening. Dutch neusgat (nose-hole) is the closest cognate to English nostril in structure. The Romance languages all inherited the Latin naris directly: French narine, Italian narice, Spanish nariz (which doubles as the general word for nose), Portuguese narina, Romanian nară. Slavic languages built their own compounds: Russian nozdrja and Polish nozdrze both descend from Proto-Slavic *nozdrьja, itself probably a compound of the *nas- root with a second element meaning hole or cavity, structurally parallel to the English form but independently invented. Modern Greek ρουθούνι (routhoúni) is a late Byzantine coinage unrelated to either the PIE or Latin lines. The world's languages overwhelmingly build the word for nostril by compounding rather than by dedicated root — evidence, perhaps, that naming the hole is always secondary to naming the nose.
Every time the word nostril is spoken, it performs a small act of linguistic archaeology. The nos- carries the Indo-European root for nose that connects English to Latin, Sanskrit, and a dozen other branches. The -tril carries the Germanic reflex of a PIE root meaning to pass through, shifted by Grimm's Law from t to þ, worn down by a millennium of use. The compound itself carries the Anglo-Saxon method of word-building: take what you have, put it together, call the thing what it is. The nose-hole. Transparent, ancient, and still doing its work.