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.
The two Alteans teach the five pilots to work as a team, and they all bond together to form Voltron and defend the universe. Shiro becomes Team Dad and The Leader. Keith and Lance form a rivalry for the Lancer role where the former is an Ace Ineffectual Loner and the latter is a Glory Hound Casanova Wannabe.