U+1E9E Latin Capital Letter Sharp S

The Wikipedia has the following information about this codepoint:

In German orthography, the letter ß, called Eszett (IPA: [ɛsˈtsɛt]) or scharfes S (IPA: [ˌʃaʁfəs ˈʔɛs], "sharp S"), represents the /s/ phoneme in Standard German when following long vowels and diphthongs. The letter-name Eszett combines the names of the letters of ⟨s⟩ (Es) and ⟨z⟩ (Zett) in German. The character's Unicode names in English are sharp s and eszett. The Eszett letter is used only in German, and can be typographically replaced with the double-s digraph ⟨ss⟩, if the ß-character is unavailable. In the 20th century, the ß-character was replaced with ss in the spelling of Swiss Standard German (Switzerland and Liechtenstein), while remaining Standard German spelling in other varieties of the German language.

The letter originates as the ⟨sz⟩ digraph as used in late medieval and early modern German orthography, represented as a ligature of ⟨ſ⟩ (long s) and ⟨ʒ⟩ (tailed z) in blackletter typefaces, yielding ⟨ſʒ⟩. This developed from an earlier usage of ⟨z⟩ in Old and Middle High German to represent a separate sibilant sound from ⟨s⟩; when the difference between the two sounds was lost in the 13th century, the two symbols came to be combined as ⟨sz⟩ in some situations.

Traditionally, ⟨ß⟩ did not have a capital form, although some type designers introduced de facto capitalized variants. In 2017, the Council for German Orthography officially adopted a capital, ⟨ẞ⟩, as an acceptable variant in German orthography, ending a long orthographic debate.

Lowercase ⟨ß⟩ was encoded by ECMA-94 (1985) at position 223 (hexadecimal DF), inherited by Latin-1 and Unicode (U+00DF ß LATIN SMALL LETTER SHARP S). The HTML entity ß was introduced with HTML 2.0 (1995). The capital ⟨ẞ⟩ was encoded by Unicode in 2008 at (U+1E9E ẞ LATIN CAPITAL LETTER SHARP S).