小 (xiǎo): Means “small” or “little.”
事 (shì): Means “matter,” “affair,” or “thing.”
一 (yī): The number “one.”
桩 (zhuāng): A measure word for events, cases, or affairs. While its original meaning is a “stake” or “post” in the ground, in this context, it functions like “an item” or “a case.”
Putting them together, 小事 (xiǎoshì) means “a small matter.” Adding 一桩 (yī zhuāng) quantifies it as “a single case of a small matter,” emphasizing its singularity and insignificance. It's a vivid way of saying something is just one, simple, unimportant thing.