The endianness of UTF16 is the same as endianness of numbers for the session.
Endianness is the byte ordering convention of data that is represented with multiple bytes. The ordering method is either big endian or little endian. For example, the big endian method indicates the number 256 as the sequence 0x01 0x00. The little endian method indicates the number 256 as 0x00 0x01.