Fortif. Forms: α. 6–7 terraplene, 7 -plana, plane, teraplene, 8–9 terraplain. β. 6 terreplaine, 8–9 -plain, 9 -pleine, 8– terreplein. [In α. ad. It. terrapieno, in Sp. terrapleno, in same sense; cf. It. terrapienare, Sp. terraplenar, to fill up with earth, f. terra earth + pieno (:—L. plēnus) full; in β. a. corresponding French terreplein. Both in F. and Eng., the second element was sometimes erroneously taken as It. piano, F. plain plane, flat, level (so in Littré), whence the former spellings -plain, plane: cf. sense 2. A form terrapin app. from It. terrapieno appears in F. in 1567 (Godefroy, Compl.); cf. TERREPLEIN v. below.]
1. Originally, The talus or sloping bank of earth behind a wall or rampart; hence, the surface of a rampart behind the parapet; and strictly, the level space on which the guns are mounted, between the banquette and the inner talus.
a. 1598. Barret, Theor. Warres, 130. Vpon these Terraplenes should trees be planted. Ibid., Gloss., 253. Terraplene, an Italian word,… the earth that is rampired and filled vp vnto the inside of any wall or bulwarke.
1688. R. Holme, Armoury, III. xvi. (Roxb.), 100/1. The Terraplane or walk of the Rampire.
1689. G. Walker, Siege of Derry, 9. The outside Wall of Stone, or Battlements above the Terra-plene is not more than two Foot in thickness.
1712. J. James, trans. Le Blond’s Gardening, 118. The Platform sustained by the Walls or Banks of the Terrasses … in Fortification, is call’d the Terra-plain.
1829. Sun, 17 Sept., 1/5. The insignificance of their batteries and the smallness of their terraplains, which prevent cannons of large calibre being placed there.
1859. F. A. Griffiths, Artil. Man. (1862), 260. The Terraplein is the upper part of the rampart, which remains after having constructed the parapet.
β. 1591. Garrard’s Art Warre, 317 (Stanf.). If … you cannot make Trauerses vppon the Terreplains, for that the Enemy doth hinder it.
1704. J. Harris, Lex. Techn., I. Terre-Plain, in Fortification, is the Platform or Horizontal Surface of the Rampart.
1830. E. S. N. Campbell, Dict. Mil. Sc., 88. The Banquette is placed behind this parapet, and the clear space left on the rampart, called its terrepleine, has been limited to about eighteen or twenty toises, terminated towards the town by a slope of 45°.
1879. Cassell’s Techn. Educ., IV. 138/1. Bastions are termed ‘full’ when the interior is level with the terre-plein of the rampart on either side of it.
transf. 1848. Blackw. Mag., July, 99/2. I went out to the narrow terre-plain over the craig.
2. The level base (above, on, or below the natural surface of the ground) on which a battery is placed in field fortifications; sometimes, the natural surface of the ground (quots. 1669, 1756, 1853).
[This latter use is manifestly connected with the mistaken derivation from plana, plaine, plain.]
1669. Staynred, Fortification, 8. The Height of the Rampire … ought to be … 18 Foot above the Terra Plana.
1756. Dict. Arts, etc., s.v. Foundery of Bells, They first dig a hole of a sufficient depth to contain the mould of the bell, together with the car or cannon under ground, and six inches lower than the terreplain where the work is done.
1828. J. M. Spearman, Brit. Gunner (ed. 2), 37. Breaching batteries … must be sunk to such a depth that the terreplein of the covered-way may coincide with the soles of the embrazures.
1853. Stocqueler, Milit. Encycl., Terre-plein, in field fortification, the plane of site or level country around a work.
1884. Mil. Engineering (ed. 3), I. II. 64. Batteries may be classed as follows, viz.: ‘Sunken batteries,’ in ground which the terreplein is sunk below the surface of the ground. ‘Elevated batteries,’ in which the terreplein is on or above the natural surface of the ground.
Hence † Terreplein (corruptly terrapin). v. Obs. rare, to furnish with a terreplein.
1672. in Fort St. George (Madras) Recds. Whither the Curtains of the Christian Town to bee strengthened and Terrapined.
