Favoured by chance
Call someone lucky and you usually mean fortune has gone their way: they survived a crash, drew the winning ticket, or happened to be in the right room when a job opened. The same adjective also marks objects and moments that seem to invite good outcomes, from a charm in a pocket to a guess that happens to be right. In current English it sits close to fortunate, but it keeps a sharper hint of chance rather than merit or planning.
The origin of the word lucky is not an Old English inheritance. It is a late medieval English formation: a borrowed noun with an ordinary native suffix clipped onto it.
A Low Countries loan
English had no native luck. Speakers of Old English talked about chance and prosperity with other material: hap, later reinforced from Old Norse; fortune, taken from French and ultimately Latin; and older native adjectives such as gesaelig, which once meant blessed or fortunate and later drifted toward silly. The noun luck arrives in the fifteenth century, almost certainly from the North Sea trading world. Standard etymologies point to Middle Dutch luc, a shortened form of gheluc or gelucke, happiness or good fortune, or to the closely related Middle Low German lücke. Modern Dutch geluk and German Glück are the obvious cousins.
Whether the first English speakers picked the noun up as a gambling term is uncertain. Some accounts float that idea; it remains a suggestion, not a documented path. The dating is firmer. The Oxford English Dictionary’s earliest evidence for the adjective is around 1450, in a Middle English note by John Metham that a certain day of the moon is lucky for people who want to go hunting. A generation later, in 1478, a letter in the Cely family papers uses a spelling locky of a man who might buy a horse. Noun and adjective appear in English almost together.
Built in English, not borrowed whole
Lucky is not a wholesale import of a Dutch adjective, even though Dutch and Low German already had matching forms: Middle Dutch luckich and geluckich, ancestors of modern gelukkig, and German glücklich. English built its own adjective on home soil from luck plus -y, the same suffix that turns cloud into cloudy or sleep into sleepy. Middle English spellings include lukky. Scots kept the word as well.
The deeper Germanic root is unknown. The luck-family of words surfaces in German dialects from about the twelfth century, apparently first in the Rhine-Frankish area, and spreads through High German and Dutch, then into English and the Scandinavian languages in the later Middle Ages. Swedish lycka, Danish lykke, and Icelandic lukka belong to the same cluster. Proposed links to German Lücke, a gap or opening and therefore a chance, or to the English verb lock, have been offered and largely set aside. A tie to German gelingen, to succeed, also fails on morphological grounds. Honest dictionaries leave the ultimate source blank.
That blank is useful. It keeps the story from collapsing into folk etymology. The suffix is transparent; the root is not.
From auspicious days to lucky dogs
The earliest English uses lean toward omen and timing. A day, a word, a star, or a beginning could be lucky in the sense of auspicious: likely to bring a good result. That sense never died. It is the one in lucky number, lucky penny, lucky heather, and the rabbit’s foot. By the late fifteenth and early sixteenth centuries the word also describes people who succeed, and then stretches to actions, voyages, and guesses that turn out well.
Over the next centuries the chance side of the meaning grew. By the 1590s, records show a sense close to occurring by chance rather than by skill. Lucky accident is in print by the 1660s. Later colloquial tags pile up: lucky dog for a person riding an unusual streak, from 1842; lucky break first as a failure that happens to work out, from 1872, and later as a billiards term, from 1884. The word can still mean simply prosperous, but the dominant modern feel is that the good result was not fully earned.
German Glück still covers both luck and happiness. English split those more cleanly: happy kept the inner state, lucky kept the roll of the dice. That split is why a lucky person need not be a happy one, and why unlucky is a sharper complaint than unhappy. The negative, formed in English with un-, follows the same late-medieval timeline as the positive.
A neighbour that filled a gap
The useful fact to keep is chronological as much as semantic. English did not always have a short everyday word for chance-favour. It imported luck from Dutch or Low German in the 1400s, then built an adjective onto it almost immediately. Parallel adjectives already existed on the continent, but the English form is a home derivation, not a copied ending. The first recorded lucky thing is not a person at all, but a hunting day on a lunar calendar. The people, and the charms they carry, came a few decades later and never quite left that oldest sense behind.