可能来自moist,潮湿的，有湿气的，-y,形容词后缀。引申词义受潮的，发霉的，散发霉臭味的。

1. Opening the door, she made a face at the musty smell.

她打开门后闻到一股难闻的霉味，不禁做了个鬼脸。

来自柯林斯例句

2. If damp, musty buildings make you ill, mould is probably the cause.

如果潮湿发霉的建筑令你生病了，霉菌很可能是病因。

来自柯林斯例句

3. The musty aroma of incense made her head swim.

熏香发霉的气味令她感到头晕。

来自柯林斯例句

4. The room smelled musty and stale.

这个房间闻起来有股发霉的陈味儿.

来自《简明英汉词典》

5. The cottage had a musty smell after being shut up over the winter.

这间村舍关了一个冬天,有一股发霉的气味.

来自《简明英汉词典》