English uses dear in several registers at once. It names a person you love, it opens a letter to someone you may never have met, and in older or British usage it still marks a high price. Those jobs look scattered until the history is set out: they grew from one inherited adjective whose earliest English senses already mixed affection with value.
The origin of the word dear is native, not a loan from French or Latin. Old English had dēore, with dialect forms such as Anglian diore and West Saxon dȳre. Middle English carried it forward as dere, deere, and deore. First-use notes in standard dictionaries place the adjective in English before 900, which is another way of saying it was already there when written Old English becomes plentiful. That Old English word did not mean only beloved. It also meant precious, costly, excellent, and even noble. Feeling and price sat in the same form from the beginning.
A West Germanic adjective
The immediate family is Germanic. Behind the Old English forms stands Proto-West Germanic diurī, from Proto-Germanic diurijaz (also cited as deurja-), reconstructed with the same double load: dear in feeling, dear in cost. The descendants still show the split in different ways. German teuer is the ordinary word for expensive. Dutch kept two heirs, dier on the affectionate side and duur on the costly one. Old Norse dýrr and the modern Scandinavian adjectives dýr and dyr lean toward price. Old Saxon diuri, Old Frisian diore, and Yiddish tayer belong to the same set. Finnish tyyris and related Finnic and Sámi words are borrowings from Germanic, not independent cousins from a shared Indo-European ancestor.
The adjective has no prefix worth unpacking in English. What it does have is a small cluster of derivatives that keep the old range in view. Darling is Old English dēorling: the adjective plus -ling, a suffix for someone marked by a quality, already in ninth-century use. Dearth comes from the scarce-and-costly side; by the thirteenth century it could name famine, a shortage that made food expensive. Dearly in Old English could mean worthily or excellently; later it meant with tender affection, and later still “at a high price,” as in paying dearly. Endear is a later formation on the same stem.
Where the deeper trail stops
Further back than Proto-Germanic, the account is not settled. Major etymological surveys treat the pre-Germanic source as unknown, and that caution is the right one. One suggestion links the adjective to a Proto-Indo-European root meaning to burn, with a supposed path from heat to warmth of feeling. Another, associated with the comparative work of Guus Kroonen, compares it to a West Germanic verb of grieving or suffering and sketches a development from something like “worth mourning” to “precious.” A third reading of the descendant meanings starts from rare or scarce rather than from affection. None of these is a consensus. Until one of them is, the honest stopping point is the Germanic adjective itself.
How the senses thinned
The later English history is less a reversal than a thinning. The sense “noble, excellent” faded and is now obsolete. The sense “costly” survived but receded. It remains familiar in British, Irish, and some New Zealand English, often with a dated or lightly humorous color, and it is still audible in pay dearly and in dearth. In most American speech, “loved” or “highly valued” became the default.
Address forms followed the affectionate side and then froze into etiquette. Vocatives such as my dear are attested from the mid-thirteenth century. As a polite opener of letters, Dear is in use from the mid-fifteenth century; from there it became a heading that need not imply warmth at all. As a noun for a loved person, it appears from the late fourteenth century, probably shortened from a phrase such as dear one.
Two later uses sit on the edge of that line. From the 1690s, oh dear and dear me work as interjections of surprise, pity, or dismay. How the adjective became a gasp is not clear; the intended sense was never recorded with any confidence. In 1945, wartime English added Dear John letter for a breakup notice sent to a man in service, taking the old epistolary formula and loading it with a very specific dread.
A look-alike, not a relative
English also has a second, now rare dear meaning severe or grievous, as in a dearest need. Dictionaries treat that adjective as a separate word. It comes from Old English dēor “brave, bold, fierce,” through Middle English dere, and only later shared a spelling with the word for beloved. It is also distinct from deer the animal, which continues a different Old English dēor meaning beast. The three histories meet as homophones. They do not share a root.
The cleanest reminder of what the main adjective once held together is still on the other side of the North Sea. Where English kept one form and let the costly sense grow old-fashioned, Dutch split the inheritance: dier for what you love, duur for what costs too much. English dear is both, and the letter heading is the polite remainder of a word that once meant something expensive enough to matter.