Emerald is a variety of the mineral beryl (Be₃Al₂(SiO₃)₆) colored green by trace amounts of chromium and sometimes vanadium. Beryl has a hardness of 7.5–8 on the 10 point Mohs scale of mineral hardness. Most emeralds are highly included, so their toughness (resistance to breakage) is classified as generally poor.

The word "Emerald" is derived (via Old French: Esmeraude and Middle English: Emeraude), from Vulgar Latin: Esmaralda/Esmaraldus, a variant of Latin Smaragdus, which originated in Greek: σμάραγδος (smaragdos; "green gem"); its original source being either the Hebrew word אזמרגד izmargad meaning "emerald" or "green" or the Sanskrit word मरकत marakata meaning "emerald." The name could also be related to the Semitic word baraq (בָּרָק ;البُراق; "lightning" or "shine") (cf. Hebrew: ברקת bareqeth and Arabic: برق barq "lightning"). It is the same source for the names Persian (زمرّد zomorrod), Turkish (zümrüt), Sanskrit (मरकत ; marakata), Kannada (ಪಚ್ಚೆ ; Pacche), Telugu (Paccha), Georgian (ზურმუხტი; zurmukhti), Russian (изумруд; izumrud) and Armenian zmruxt.

Caroline Esmeralda van der Leeuw (b. 26 April 1981 in Amsterdam), best known by her stage name, Caro Emerald, is a Dutch jazz singer. She debuted on 6 July 2009 with her single "Back It Up". Her debut album Deleted Scenes from the Cutting Room Floor set a new all-time chart record on 20 August 2010, spending its 30th week at number one on the Dutch album chart, beating the previous record set by Michael Jackson's Thriller by one week. The album has become the biggest selling album of 2010 in the Netherlands, selling over 300,000 copies so far. In total more than a million copies have been sold so far. On 3 October 2010, Van der Leeuw was awarded the Dutch Music Prize "Edison Award" for Best Female Artist.

Caroline Esmeralda van der Leeuw was born on 26 April 1981 in Amsterdam, the Netherlands. She was trained as a jazz vocalist at the Amsterdam Conservatory, graduating in 2005.

In early 2007 Dutch producer Jan van Wieringen invited van der Leeuw to sing the vocal on a demo track he was co-producing with songwriter/producer David Schreurs. The song, "Back It Up", had been written by Schreurs together with Canadian songwriter Vince Degiorgio, and was based on a hip-hop beat created by Jan and Robin Veldman. Caro's jazzy vocal style was considered a "perfect match" for the new song.