This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 矤 is uncertain. It visually combines 弓 (bow) and 矢 (arrow), but its original meaning and component function are unclear.
With a bow 弓 and an arrow 矢, 矤 looks like archery equipment, but its actual meaning is unknown. Think of it as a mysterious archery kanji.
For シン, imagine a shin guard worn by an archer: shin -> シン, protecting the leg while drawing the bow 弓 and arrow 矢.