The unglossed headword phrase, in the (nominative) singular, is apparently generated by the one which constitutes the body of the entry; there both nouns, as indicated, are plurals.
[1] The phrase, again at mu 1209, is nowhere else attested in this precise form; rather, as Adler noted, it seems to be an approximation (or derivative) of Cassius Dio 46.36.4, e)s e)lasmo\n molu/bdou lepto\n e)ggrayante/s tina (of a secret message). On the same theme note also [DW] Aeneas Tacticus 31.7, ei)senexqei/h d' a)\n grafh\ kai\ e)n toi=s tw=n gunaikw=n w)si\n ... e)lasmou\s e)neilhme/nous leptou\s molibdi/nous.