The siesta is named after a Roman clock

The Romans divided daylight into twelve hours, counted from dawn. The «hora sexta» — the sixth hour — fell right at midday, when the sun bears down and working in the Mediterranean becomes a bad idea. Resting at that moment was keeping the sixth hour: from «sexta» came «siesta».

So the siesta isn't named after sleeping, but after the hour at which one sleeps. First it was a position of the sun; then a custom; finally a noun with its own verb, «sestear» — to take one's siesta.

The word turned out to be one of Spanish's greatest exports: English, French, German and half the world say «siesta», usually without bothering to translate it.

Some empires leave aqueducts. This one left, among other things, an official time for lying down.