In a way that is well-suited, appropriate, or brings happiness; in a fortunate or apt manner.
From felicitous (appropriate, well-suited, fortunate) plus the adverb-forming suffix -ly. Felicitous derives from Latin felicitas via French, emphasizing appropriateness rather than chance.
A word chooses its moment felicitously when it's perfectly timed and exactly right—authors love this word because it describes that magical moment when something fits just perfectly, like the exact right metaphor appearing exactly when needed.
Complete word intelligence in one call. Free tier — 50 lookups/day.