His excuse had a certain plausibility at first, but fell apart upon closer examination.

plausibility 是名词，由形容词 plausible（看似合理的）加上名词后缀 -ibility 构成。plausible 来自拉丁语 plausibilis（值得鼓掌的），引申为"看似可信的"。plausibility 指"表面上的可信度"或"貌似合理性"。