What 흿 means
Its meaning comes from its Korean word, not the block alone.
Hangul represents Korean speech by placing an initial consonant, a vowel, and sometimes a final consonant in one square syllable block. In 흿, ㅎ begins the block, ㅢ is the vowel, and final ㅅ closes it.
Hunminjeongeum, the book explaining Hangul's creation and principles, was first published in 1446. That date documents the writing system's design, not the first appearance of every possible syllable. Korean typefaces can shift the spacing of the letters inside the square; the spacing changes the look, not the syllable.
It belongs in Korean text; alone, it gives readers a syllable without the word or sentence needed to interpret it.
Don't confuse it with
2Questions people ask
1Why does ㅢ in 흿 sound like ㅣ?
In standard Korean, ㅢ after an initial consonant is pronounced like ㅣ, so the vowel in 흿 has that sound. The spelling still uses ㅢ.
How to type 흿
흿\D77FCodes and encoding1 code points
A visible symbol can contain several code points. JS .length counts UTF-16 units; UTF-8 counts bytes.