Luxembourgish is a Germanic language spoken by about 390,000 people in Luxembourg (Lëtzebuerg), France (Frankräich), Belgium (Belsch) and Germany (Däitschland). There are also a few Luxembourgish speakers in the USA. It has a lot in common with German and Dutch, and has also borrowed some words from French, e.g. merci (thank you).
Luxembourgish has been spoken since Frankish times (c. 1,000 AD), along the banks of the Moselle. Literature in Luxembourgish flourished during the 19th century. Luxembourgish started to be used as a language of instruction in schools in 1914. A new spelling system, Lëzebuurjer Ortografi, was devised by Jean Feltes, a phonetician, in 1946, though it never really caught on. In 1950 Joseph Tockert, Helene Palgen, and Robert Bruch were commissioned to produce a new Luxembourgish dictionary. They invented a new spelling system for the dictionary, which was adopted as the official one in 1976, when Feltes' system was dropped.
source
wikipedia.org,
omniglot.com,
evertype.com &
ethnologue.com