A word for difficulty and unrest
In modern English, trouble covers a wide patch of discomfort. As a noun it can mean a hard situation, a source of worry, public unrest, extra effort, a health problem, or a brush with the law. As a verb it can mean to worry someone, to afflict the body, to stir water, or — in a milder register — to put a person to a small inconvenience. Those uses look scattered until the older picture is restored: the word began as a way of talking about agitation, whether of the mind or of a liquid.
The origin of the word trouble is a French borrowing, not a native Germanic inheritance. Both the noun and the verb are already visible in English around 1230, in early Middle English religious prose. The verb turns up in the Ancrene Riwle; the noun is recorded from about the same date in Hali Meidenhad. Surveys often round the arrival to about 1200. Either way, the word is in place early in the thirteenth century, once French had become a regular source for English vocabulary.
From Old French into Middle English
English took the verb from Old French trubler, troubler, trobler — forms of a verb already current by the eleventh century. Those spellings are not the original French shape. They are metathetic variants of torbler, tourbler, turbler: the r and the vowel have swapped places. The Oxford English Dictionary treats the English verb as a borrowing from French trubler. The Middle English Dictionary lists a crowd of spellings that show the same unsettled cluster: troublen, trublen, troblen, troubelen, and more besides.
The noun followed the same route. Old French had truble and torble for disturbance; Middle English trouble and troble come from that noun, itself built on the verb. For a time English also kept a form that had not undergone the swap: turble, from Old French torble or tourble, is attested in the early fifteenth century with the sense of agitation or tumult. That sister form later dropped out, leaving the metathesized trouble as the survivor.
Modern French still has troubler: to disturb order or sleep, to unsettle a person, and, reflexively, of water turning cloudy or a sky growing overcast.
The Latin knot: mud, crowds, and confusion
Behind the French verb stands a reconstructed Vulgar Latin turbulare or turbulāre. Dictionaries do not tell a single story about how that form was built, and the disagreement is worth stating plainly.
One line, followed by the Online Etymology Dictionary, derives it from Late Latin turbidare, to make turbid, from classical Latin turbidus — muddy, confused, full of disorder. John Ayto’s account is close: Vulgar Latin turbulus as an alteration of turbidus, then turbulāre from that adjective. Another line, visible in Wiktionary, takes Latin turbula, a diminutive of turba meaning a small or disorderly group of people, as the immediate source. The American Heritage Dictionary joins the two: turbulāre is an alteration of Late Latin turbidāre, influenced by turbula.
What is not in dispute is the deeper Latin family. Turbidus and turbula both belong with turba, a crowd or tumult, and with the verb turbare, to disturb. English disturb comes from Latin disturbare on the same stem; turbid, turbulent, and turbine are later relatives. The image underneath is physical: sediment stirred so that water is no longer clear, a crowd that turns a place into noise.
How far the Latin noun itself goes is less certain. Turba resembles Greek túrbē, disorder, and some handbooks treat the Latin word as a borrowing from Greek. The Latinist Michiel de Vaan notes that the Greek forms look like loanwords too, and that Latin may have taken turba from a third source rather than straight from Greek. The family is already well developed in Plautus, which suggests the word had been in Latin for some time. A neat Proto-Indo-European reconstruction is not something the sources agree on, so it is better left unclaimed.
From cloudy water to polite apology
The oldest French senses of the verb include making something cloudy, stirring it, mixing it. Middle English kept that concrete use. The verb could mean to muddy water, stir the lees of wine, roughen the sea, or unsettle the air. Biblical English of the late fourteenth century uses it of water stirred with the feet. Figurative extensions sit beside that: eyes or the moon growing dim, knowledge losing clarity, a forehead furrowed rather than smooth.
The earliest English noun sense is mental: agitation of the mind, emotional turmoil. By the mid-fourteenth century the verb can mean to inflict suffering. Around 1400 the word spreads to confusion and disorder in general, and to the sea. In the early fifteenth century the noun can name a concern, a cause for worry; by the 1590s it can name the thing that produces the worry. Unpleasant dealings with the authorities appear in the mid-sixteenth century. The lighter sense — to pester with requests, often in formulas of polite apology such as may I trouble you — is in place by the 1510s. That last shift is a social thinning of the old meaning: the same verb that once stirred sediment now asks a small favour.
Later English packed still more into the noun: a fault in a mining stratum; Cockney rhyming slang trouble and strife for a wife, recorded from 1908; dated slang for an unwanted pregnancy. The Troubles as a label for Irish political violence is attested from 1880 with reference to the 1640s, and later became the usual name for the Northern Ireland conflict from the late 1960s.
Middle English also ran derivatives that later dropped away: troublance for hindrance, troubleness for turbulence or opacity, troubliness for turbidity. Those lost nouns still advertise the old link between cloudy liquid and public disorder.
What the relatives still show
French troubler, Catalan tèrbol, Occitan trebolar, and Romanian tulbura / tulbure keep the same Latin disturbance in other Romance languages, often with the watery sense still visible. English speakers who never think of mud when they say trouble still use turbid for water that has been stirred. That split is the useful remainder of the history: one branch kept the literal sediment, the other kept the feeling of being stirred. The metathesis in Old French hid the turba family from ordinary sight, which is why trouble no longer looks like turbulent even though they share a root.