This is the 5901st most frequent Japanese word.
みなぎる
To be full of, to overflow, or to surge with (emotion, energy, etc.).
Here, "みなぎる" is used to describe the overflowing abundance of his confidence, emphasizing its intensity and pervasive nature.
彼の自信は体中にみなぎっていて、目からも感じ取れるほどだった。
His confidence was overflowing through his entire body, so much that one could feel it from his eyes.
In this sentence, "みなぎる" illustrates the overflowing nature of the lake's water, symbolizing physical and visible abundance.
湖の水がみなぎって岸辺にまで達していた。
The lake's water overflowed and reached the shores.
This usage of "みなぎる" conveys the idea of the hall being metaphorically filled with anticipation, emphasizing its collective emotional presence.