The ordinary meaning of nap is to doze off during the day. The secondary meaning is to be offguard. Hence the phrase Catch them napping . Flying by the nap of the earth refers to the practice of flying low to the earth (undetected by radar) to catch the enemy by surprise (or napping).
the tribunes The Tribunes were elected representatives that protected the plebeians from mistreatment. The Tribunes attended meetings of the consuls or Senate in an attempt to bring justice to the plebeians.
In ancient Rome, there were different types of tribunes, including military tribunes, consular tribunes, and plebeian tribunes. The word tribune is connected with the word tribe, in Latin (tribunus and tribus) just as in English. Originally, a tribune represented a tribe; later, tribune refers to a variety of officers. Here are three of the main types of tribunes you'll find in reading ancient Roman history.