Rare, literary term for a nickname or alias. The cross-reference 綽名 (しゃくめい) is a more common synonym. This word is seldom used in modern Japanese; あだ名 or ニックネーム are the usual terms.
See also: あだ名
The word 綽号 can be found in old documents, but it is hardly used today.
The exact derivation is uncertain. The kanji 綽 (しゃく) means 'loose' or 'generous' and is rare; 号 (ごう) means 'name' or 'title'. The combination may have been used historically to refer to an informal or alternate name.