wear, put on (a sword)
佩 centers on attaching something to one's body, especially wearing or putting on an item like a sword at the waist.
佩 combines 亻 (person) with a right side that likely represents an ornament or item worn at the waist. The exact historical development of the right component is uncertain.
A person 亻 wears a cloth belt 巾 with a sword hanging from it, like an ornament on a stand 几. Together, 佩 means to wear or put on a sword.
For ハイ, imagine a person wearing a sword and giving a high-five: high -> ハイ, as they proudly display their worn weapon.