This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
夶 is a rare character composed of two 大 (big) elements side by side. Its exact historical origin and development are uncertain.
Two big figures standing side by side, perhaps comparing their size or strength.
For ヒ, imagine two big figures comparing their height: 'He' is taller, so 'he' (ヒ) wins the comparison.