Waddell is of Scottish origin, derived from the Old Norse personal name 'Valdi' which means 'ruler'. It was also a Scottish family name, particularly prevalent in the southwest of Scotland. The surname Waddell is believed to have originated as a nickname for someone who lived near a waterfall or stream, as it evolved from the Old English word 'wædels', meaning 'waterfall'.
The name Waddell experienced notable fluctuations in popularity over the years, with a significant increase during World War I and a peak in the late 1920s to early 1930s. However, it began declining consistently from the mid-1930s onwards, becoming quite uncommon by the 1950s and remaining so until present times.