尢 is the Kangxi radical for "lame" and depicts a person with bent legs. In 尤 it forms the main body — three strokes — and indexes the character. Same radical heads a small family including 就, 尧, 尴.
丶 is a dot stroke functioning as a marker — added to 尢 to differentiate this character. The dot doesn't carry independent meaning here; it's a positional indicator that turned the lame-person graph into the modern "especially, particularly" word.
