an embroidered pennant
旐 refers specifically to a type of embroidered pennant or banner, likely used in ceremonial or military contexts.
旐 combines the flag radical 方 with the phonetic component 兆, suggesting a type of banner whose name is related to the sound of 兆.
The flag radical 方 on the left indicates a banner, and the component 兆 inside suggests a sign or omen. Picture an embroidered pennant used to signal an important event.
For チョウ, imagine a long embroidered pennant fluttering in the wind, and think of the sound 'choh' as it snaps: Chou -> チョウ.