The article examines two expressions for the new moon in Latin, luna silens and luna sicca (or sitiens). Despite the unusual imagery behind the choice of these epithets, the expressions appear in unremarkable, technical contexts (mostly, in works on agriculture by Cato, Columella, Pliny the Elder) and denote this particular phase of the lunar cycle without any indication that the metaphors were perceived by speakers. The paper aims at explaining this paradox. It is shown that neither of these expressions was based on superstitions or popular lore. They reflected, in fact, an attempt to present the phase of the lunar cycle when the moon is invisible in contrast to other visible phases, which are easier to identify. Thus, luna silens was created by opposition to luna crescens “the waxing moon”, as denoting the moment before active, visible growth will begin. Luna sicca, on the other hand, was created by opposition to luna plena, “the full moon”, where the moon would be imagined as a vessel, gradually filled to its fullness by white light. Finally, luna sitiens was an expression, synonymic to luna sicca, created by analogy with luna silens. While these expressions were used as terms without any artistic effect, Augustan poets seem to have recognized their poetic potential and, on some occasions, put it to use (in particular, Verg. Aen. 2, 255 and Prop. 2, 17, 15).