"pertaining to the ancient Roman mile," 1640s, from Latin milliarius, from mille (see mile (n.)). As a noun, "a milestone," c. 1600, from Latin milliarium.
Entries linking to milliary
unit of linear measure in Great Britain, the U.S., and a few other countries, formerly used in most European countries before the metric system; Old English mil, from West Germanic *milja (source also of Middle Dutch mile, Dutch mijl, Old High German mila, German Meile), from Latin milia "thousands," plural of mille "a thousand" (neuter plural was mistaken in Germanic as a fem. singular), which is of unknown origin.
The Latin word also is the source of French mille, Italian miglio, Spanish milla. The Scandinavian words (Old Norse mila, etc.) are from English. An ancient Roman mile was 1,000 double paces (one step with each foot), for about 4,860 feet, but many local variants developed, in part in an attempt to reconcile the mile with the agricultural system of measurements. Consequently, old European miles were of various lengths. The medieval English mile was 6,610 feet; the old London mile was 5,000 feet. In Germany, Holland, and Scandinavia in the Middle Ages, the Latin word was applied arbitrarily to the ancient Germanic rasta, a measure of from 3.25 to 6 English miles. In England the ordinary mile was set by legal act at 320 perches (5,280 feet) by statute in Elizabeth's reign.
In Middle English the word also was a unit of time, "about 20 minutes," roughly what was required to walk a mile. The word has been used generically since 1580s for "a great distance." Mile-a-minute (adj.) "very fast" is attested from 1957 in railroad publications (automobiles had attained 60 mph by 1903).