Are We Heading Towards Another...
Politics2 mins ago
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For more on marking an answer as the "Best Answer", please visit our FAQ.The body-art variation derives from the Tahitian tatu or tatau, which means to mark or strike (the latter referring to traditional methods of applying the designs). See Wikipedia article.
In the military sense, the word comes from the last order and closing time shouts in Dutch, or horn signals, meaning "Doe den tap toe", or just "tap toe", heard across The Netherlands in the 18th and 19th Century, and which means "turn off the taps". Again, Wikipedia to the rescue.