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ellipse [ellipse 词源字典]: ellipse: [18] Greek élleipsis meant literally ‘defect, failure’. It was a derivative of elleípein, literally ‘leave in’, hence ‘leave behind, leave out, fall short, fail’, a compound verb formed from the prefix en- ‘in’ and leípein ‘leave’ (which is related to English loan and relinquish). It was borrowed into English in the 17th century as ellipsis in the grammatical sense ‘omission of a word or words’, but its mathematical use for an ‘oval’ (enshrined in the form ellipse, borrowed via French ellipse and Latin ellīpsis) comes from the notion that a square drawn on lines passing vertically and laterally through the centre of an ellipse ‘falls short’ of the entire length of the lateral line.
=> loan, relinquish[ellipse etymology, ellipse origin, 英语词源]
drop (v.): Old English dropian "to fall in drops" (see drop (n.)). Meaning "to fall vertically" is late 14c. Transitive sense "allow to fall" is mid-14c. Related: Dropped; dropping. Exclamation drop dead is from 1934; as an adjective meaning "stunning, excellent" it is first recorded 1970.
vertical (adj.): 1550s, "of or at the vertex, directly overhead," from Middle French vertical (1540s), from Late Latin verticalis "overhead," from Latin vertex (genitive verticis) "highest point" (see vertex). Meaning "straight up and down" is first recorded 1704. As a noun meaning "the vertical position or line" from 1834. Related: Vertically.