boundary
疆 centers on a dividing line between areas: a boundary or border. The given meaning "boundary" is the core idea.
疆 combines 土 (earth) with 畺, which itself contains 田 (field) and 弓 (bow), suggesting a boundary marked on the land. The exact historical development is uncertain, but the component 畺 likely reinforces the idea of a measured or drawn border.
The left side 土 is earth, and the right side 畺 looks like a field 田 with a measuring line 弓. Picture drawing a boundary line across the land to separate fields.
For キョウ, imagine a border guard shouting "KYOU!" (like "kyo!") when you cross the boundary: the sharp sound cues キョウ and marks the line.
Xinjiang Uyghur Autonomous Region (China)