What 숬 means
It is one Korean syllable; its surrounding word gives it meaning.
Hangul builds syllable blocks from letters called jamo. In 숬, ㅅ begins the block, ㅜ is its vowel, and ㅆ is its final consonant. Fonts may draw the block differently without changing its text identity.
Before Hangul, Korean writing used Chinese characters and the Idu system, which adapted them for Korean. King Sejong created the new script in 1443 under the name Hunminjeongeum; an explanatory guide of that name appeared in 1446. Hangul became the official writing system in Korea in 1894.
Questions people ask
1Why does 숬 show as a box on some devices?
Because that device's fonts have no glyph for it. The character is still correct and still copies correctly — the box is a missing glyph, not a broken character.
How to type 숬
숬\C22CCodes and encoding1 code points
A visible symbol can contain several code points. JS .length counts UTF-16 units; UTF-8 counts bytes.