The original meaning of military tattoo is a military drum performance, but nowadays it sometimes means army displays more generally.
It dates from the 17th century when the British Army was fighting in the Low Countries (Belgium and the Netherlands). Drummers from the garrison were sent out into the towns at 21:30 hrs (9:30PM) each evening to inform the soldiers that it was time to return to barracks. The process was known as doe den tap toe (Dutch for "turn off the tap"), an instruction to innkeepers to stop serving beer and send the soldiers home for the night. The drummers continued to play until the curfew at 22:00 hrs (10:00PM). Tattoo, earlier tap-too and taptoo, are alterations of the Dutch words tap toe which have the same meaning.
Over the years, the process became more of a show and often included the playing of the first post at 21:30 hrs and the last post at 22:00. Bands and displays were included and shows were often conducted by floodlight or searchlight. Tattoos were commonplace in the late 19th century with most military and garrison towns putting on some kind of show or entertainment during the summer months. Between the First World War and the Second World War elaborate tattoos were held in many towns, with the largest in Aldershot.
One of the best known Tattoos is held on the Esplanade in front of Edinburgh Castle each August and forms the centrepiece of the annual Edinburgh Festival. The Edinburgh Military Tattoo was first staged in 1950; it combines the traditional sounds of the bagpipes and drums with the modern aspects of the armed forces.