firmamentum

Etymology
From, from. lit. 'that which strengthens or supports'. The meaning of "a strengthening, support, prop", especially in the figurative sense (of an argument etc., ) is classical, and frequently occurs in Cicero.

The cosmological sense is coined in the Vulgate in imitation of LXX, which in turn translates. Some have viewed this as a mistranslation and the modern New American Standard Bible translates this as "expanse" — based on a modern scientific bias. However, ancient Hebrews — including those who translated the Hebrew Bible into Greek (the Septuagint or LXX) — understood this term to refer to solid material. Hence, the LXX. The Hebrew, refers to a hard substance that has been hammered out by crafstmen (Exodus 39:3; Isaiah 40:19; compare Job 37:18, Exodus 24:10, Ezek. 1:22). Ancient Hebrews, in line with their Mesopotamian neighbors, understood the "firmament" or "sky" as a dome, over which was a layer of water, under which rotated the sun, moon, and stars (Gen. 1:6-8, 14-15). The Genesis creation account is accommodated to this pre-scientific understanding of the sky as a dome, with a layer of cosmic waters above and the stellar constellations below.

Noun

 * 1) A strengthening, support, prop, stay.
 * 2) The firmament; the sky fixed above the earth.
 * 3) * Vulgate: Genesis 1,7-8
 * Et fecit Deus firmamentum divisitque aquas, quae erant sub firmamento, ab his, quae erant super firmamentum. [8] Vocavitque Deus firmamentum Caelum.
 * And God made the firmament and divided the waters, that were under the firmament, from those, that were above the firmament. [8] And God called the firmament the sky.
 * 1) The main point or crux.