late 14c., champertie, champartie, the illegal act whereby a person not otherwise interested makes a bargain to maintain a litigant in return for a share of the property in dispute if the case succeeds, from Old French champart "portion of produce received by a feudal lord from land held in lease from him" (13c.), from Medieval Latin campipartem, from campi pars "part of the field" (see campus + part (n.)).
mid-15c., "transference of property, grant of land for life or a period of years," via Anglo-French from Old French demis, fem. past participle of desmetre "dismiss, put away" (Modern French démettre), from des- "away" (from Latin dis-) + metre "put," from Latin mittere "let go, send" (see mission).
Originally especially "a conveyance of an estate by will or lease," then "transfer of sovereignty," as by the death or deposing of a king (1540s). The sense was transferred to "death" (as the occasion of such a transfer) by 1754, at first especially the death of a sovereign or other important person, but also as a euphemism for "death."
mid-15c., "act of granting or yielding" (especially in argumentation), from Old French concession (14c.) or directly from Latin concessionem (nominative concessio) "an allowing, conceding," noun of action from past-participle stem of concedere "to give way, yield," figuratively "agree, consent, give precedence," from con-, here perhaps an intensive prefix (see con-), + cedere "to go, grant, give way" (from PIE root *ked- "to go, yield").
From 1610s as "the thing or point yielded." Meaning "property granted by government" is from 1650s. Sense of "grant of privilege by a government to individuals to engage in some enterprise" is from 1856, from a sense in French. Hence the meaning "grant or lease of a small part of a property for some specified purpose" (1897), the sense in concession stand "snack bar, refreshment stand."
c. 1300, "fixed payment (usually in exchange for taxes collected, etc.), fixed rent," from Old French ferme "a rent, lease" (13c.), from Medieval Latin firma "fixed payment," from Latin firmare "to fix, settle, confirm, strengthen," from firmus "strong; stable," figuratively "constant, trusty" (from suffixed form of PIE root *dher- "to hold firmly, support").
Sense of "tract of leased land" is first recorded early 14c.; that of "cultivated land" (leased or not) is 1520s. A word of confused history, but there is agreement that "the purely agricultural sense is comparatively modern" [Century Dictionary]. There is a set of Old English words that appear to be related in sound and sense; if these, too, are from Latin it would be a very early borrowing. Some books strenuously defend a theory that the Anglo-Saxon words are original (perhaps related to feorh "life").
Phrase buy the farm "die in battle," is from at least World War II, perhaps a cynical reference to the draftee's dream of getting out of the war and going home, in many cases to a peaceful farmstead. The simple term buy it as slang for "suffer a mishap," especially "to die" is attested by 1825, and seems to have been picked up in airmen's jargon. Meanwhile fetch the farm is prisoner slang from at least 1879 for "get sent to the infirmary," with reference to the better diet and lighter duties there.