large, great, grand, glorious, distinguished
丕 centers on greatness in scale or status: something large, grand, glorious, or distinguished.
丕 is an ancient character whose exact origin is uncertain. It is often explained as 不 with an added horizontal stroke 一, possibly to emphasize greatness or distinction, but the historical development is not clearly established.
The top 不 looks like a person standing tall, and the bottom 一 is a solid foundation. Together they suggest something large and grand, like a distinguished figure on a pedestal.
For ヒ, imagine a grand, distinguished person letting out a hearty laugh: hee -> ヒ. The great 丕 figure chuckles with a hee sound.