See also mu 1225, also in the nominative plural.
The term properly designates a light-armed soldier, who wears only a belt carrying a dagger, and no other arms. The word is frequent in the Septuagint (ten instances), e.g. 2 Kings [4 Kingdoms] 5:2, where the NIV has "bands" and the KJV "companies"; it refers to enemy armies, e.g. from Syria or Moab.
LSJ s.v. attributes the definition "girt up alone, i. e. journeying alone" to "Suid. etc.". Such a definition is not apparent here (and is instead apparently taken across from the usage of oi)o/zwnos in mu 1225), but the second phrase is consistent with irregular troops travelling light. The negative colouring is already in place in Ephraem the Syrian, Questions and Answers p. 242 Frantzoles: "Who are the ones called 'with a single belt'?" "Murderers and brigands and any criminal and fornicator is called 'with a single belt'."
Hesychius mu1618 glosses the word "the enemies' spies, or battle-ready troops, whom we call gladiators (or, "fighters in single combat" -- but cf. mu 1231)."