wart, tumor, goiter, papule
肬 centers on abnormal skin growths: a wart, a small tumor, a goiter, or a papule. All meanings share the idea of a raised, unwanted bump on the body.
肬 combines ⺼ (flesh/body part) with 尤, which likely contributes a phonetic element. The exact historical development is uncertain, but the structure suggests a body-related growth.
The left side ⺼ is flesh, and the right side 尤 looks like a bumpy shape. Picture a fleshy bump on the skin: a wart or tumor.
For ユ, imagine you noticing a wart on your skin: you -> ユ, and you point at the fleshy bump.