This character is a Other Letter and is mainly used in the Ogham script.
The glyph is not a composition. 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+1691 forms with similar adjacent characters prevents a line break inside it.
The Wikipedia has the following information about this codepoint:
Onn is the Irish name of the seventeenth letter of the Ogham alphabet, ᚑ, meaning "ash-tree", which is related to Welsh onn(en), from the root was *ōs-, *osen 'ash'. Its phonetic value is [o].
The letter's Bríatharogam kennings are the following:
congnaid ech "wounder of horses"
féthem soíre "smoothest of craftsmanship"
lúth fían "[equipment] of warrior bands"
These refer to different uses of ashwood as horsewhips, wood used by carpenters, and for spears. In the Old Irish period, onn "ash" was replaced by uinnius. McManus takes this as an indication that the Ogham letter names date to the Primitive Irish period.
Representations
System
Representation (click value to copy)
Nº
5777
UTF-8
E1 9A 91
UTF-16
16 91
UTF-32
00 00 16 91
URL-Quoted
%E1%9A%91
HTML hex reference
ᚑ
Wrong windows-1252 Mojibake
áš‘
Encoding: GB18030 (hex bytes)
81 34 AE 31
RFC 5137
\u'1691'
Bash and Zsh inside echo -e
\u1691
C and C++
\u1691
C#
\u1691
CSS
\001691
Excel
=UNICHAR(5777)
Go
\u1691
JavaScript
\u1691
Modern JavaScript since ES6
\u{1691}
JSON
\u1691
Java
\u1691
Lua
\u{1691}
Matlab
char(5777)
Perl
"\x{1691}"
PHP
\u{1691}
PostgreSQL
U&'\1691'
PowerShell
`u{1691}
Python
\u1691
Ruby
\u{1691}
Rust
\u{1691}
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