TATTOO, a signal given by beat of drum and call of bugle at nightfall for soldiers to go to quarters when in garrison or to tents when in the field. The earlier word is taptoo or taptow, and was borrowed from Du. taptoe; the phrase de taptoe slaan, to close the taps, and the parallel Ger. Zapfenstreich, literally " tap-stroke " (Zapf, a tap of a cask), show that it meant originally a signal that the " taps " or public-houses were closed for the night.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)