BOCU-1
From Just Solve the File Format Problem
Unicode character encoding. It is associated with the ICU software, and apparently owned and patented by IBM. It is designed for small size (especially when encoding code points that are mostly from the same language), compatibility with MIME "text" media types, and to have certain desirable sorting characteristics.
BOCU-1 (Binary Ordered Compression for Unicode) is a
Despite its name, it does not have many of the attributes typical of a data compression format. It should probably be thought of simply as a Unicode encoding.
See also SCSU, to which it is sometimes compared.