Tremulously is the adverb from tremulous: it tells you that an action was done with a small shaking, and almost always that fear, nerves, weakness, or held-back tears caused it. It sits next to verbs of speaking, smiling, breathing, and reaching — 'she spoke tremulously', 'he smiled tremulously', 'the candle burned tremulously'. Because it packs both the physical shaking and the emotion behind it into one word, writers reach for it at moments when a character is barely holding together. It is quite literary; you meet it in novels far more than in conversation, and using it in ordinary speech will make you sound like a character in a book. In real talk people simply say 'in a shaky voice' or 'her hand was shaking'. Note also that it can describe light or water quivering, with no person and no emotion at all.

顫抖地、哆嗦地 (帶著緊張或害怕的細微發抖)。文學用語，口語會說 in a shaky voice