What does "kinglet" mean?

Kinglet: (Zoöl.) Any one of several species of small singing birds of the genus Regulus and family Sylviidæ. Note: The golden-crowned kinglet (Regulus satrapa), and the rubycrowned kinglet (R. calendula), are the most common American species. The common English kinglet (R. cristatus) is also called golden-crested wren, moonie, and marigold finch. The kinglets are often popularly called wrens, both in America and England.