Interpreted to mean, "May this be no omen." or "May this not be an omen." "Let there be no evil omen [because of the word just used]."
A reference to the superstition that the mere mention of some evil could make it happen.
The Romans, who were strong believers in divination, had soothsayers who were available to interpret omens as a means of foretelling the future. In fact, soothsayers (diviners) were so popular that the Romans had many words for these practitioners, among them: auspex and haruspex.
An auspex relied on observation of birds and their behavior to foretell the future, and we have inherited this word as “auspices, auspicious,” and “inauspicious”.
A haruspex divined the future by examining the entrails of sacrificed animals and also made interpretations based on the observation of lightning and other natural phenomena.