This character is a Other Letter and is commonly used, that is, in no specific script. The character is also known as fourth transfinite cardinal.
The glyph is a compatibility version of the glyph Hebrew Letter Dalet. It has no designated width in East Asian texts. In bidirectional text it is written from left to right. When changing direction it is not mirrored. The word that U+2138 forms with similar adjacent characters prevents a line break inside it. The glyph can be confused with one other glyph.
The Wikipedia has the following information about this codepoint:
Dalet (dāleth, also spelled Daleth or Daled) is the fourth letter of the Semitic abjads, including Arabic dālد, Aramaic dālaṯ 𐡃, Hebrew dāletד, Phoenician dālt 𐤃 and Syriac dālaṯ ܕ (in abjadi order; 8th in modern order). Its sound value is the voiced alveolar plosive ([d]).
The letter is based on a glyph of the Proto-Sinaitic script, probably called dalt "door" (door in Modern Hebrew is delet), ultimately based on a hieroglyph depicting a door:
Representations
System
Representation (click value to copy)
Nº
8504
UTF-8
E2 84 B8
UTF-16
21 38
UTF-32
00 00 21 38
URL-Quoted
%E2%84%B8
HTML hex reference
ℸ
Wrong windows-1252 Mojibake
ℸ
HTML named entity
ℸ
alias
fourth transfinite cardinal
Encoding: GB18030 (hex bytes)
81 36 C0 36
LATEX
\daleth
RFC 5137
\u'2138'
Bash and Zsh inside echo -e
\u2138
C and C++
\u2138
C#
\u2138
CSS
\002138
Excel
=UNICHAR(8504)
Go
\u2138
JavaScript
\u2138
Modern JavaScript since ES6
\u{2138}
JSON
\u2138
Java
\u2138
Lua
\u{2138}
Matlab
char(8504)
Perl
"\x{2138}"
PHP
\u{2138}
PostgreSQL
U&'\2138'
PowerShell
`u{2138}
Python
\u2138
Ruby
\u{2138}
Rust
\u{2138}
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