elongation (n.)

c. 1400, elongacioun, in astronomy, "angular distance of a planet from the sun as it appears from the earth;" early 15c., "extension, spreading," from Medieval Latin elongationem (nominative elongatio), noun of action from past-participle stem of Late Latin elongare "remove to a distance," from assimilated form of Latin ex "out" (see ex-) + longus "long" (see long (adj.)).