1590s, "blue pigment made from lapis lazuli," from Medieval Latin ultramarinus, literally "beyond the sea," from Latin ultra- "beyond" (from suffixed form of PIE root *al- "beyond") + marinus "of the sea," from mare "sea, the sea, seawater," from PIE root *mori- "body of water." Said to be so called because the mineral was imported from Asia.
Proto-Indo-European root meaning "body of water."
It forms all or part of: aquamarine; Armorica; beche-de-mer; cormorant; mare (n.2) "broad, dark areas of the moon;" marina; marinate; marine; mariner; maritime; marsh; mere (n.1) "lake, pool;" Merlin; mermaid; merman; meerschaum; meerkat; morass; Muriel; rosemary; submarine; ultramarine; Weimar.
It is the hypothetical source of/evidence for its existence is provided by: Latin mare; Old Church Slavonic morje, Russian more, Lithuanian marės, Old Irish muir, Welsh mor "sea;" Old English mere "sea, ocean; lake, pool," German Meer "sea."