The optative mood is a mood that indicates a wish or hope. It is similar to the cohortative in Hebrew, and closely related to the subjunctive mood. (GGBB p. 480)
“There are less than 70 optatives in the entire NT. In general, it can be said that the optative is the mood used when a speaker wishes to portray an action as possible. It usually addresses cognition, but may be used to appeal to the volition. Along with the subjunctive and imperative, the optative is one of the potential or oblique moods.” (GGBB p. 480)