This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 芘 is uncertain. It visually combines the grass radical 艹 with 比, but the original semantic and phonetic roles are unclear.
The top 艹 suggests a plant, and the bottom 比 suggests comparison or lining up. Imagine a row of identical plants being compared, but remember the meaning is uncertain.
For ヒ, picture a row of plants (艹) being compared (比) and one plant saying 'hee!' (ヒ) because it's the tallest. The sound 'hee' cues ヒ.
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