swagger [E16th] A bulging bag is the link between swagger and swag [ME]. This is what swag originally meant, and it later led to the word being used as a verb in the sense ‘to make something sway or sag’. Swagger appears to have developed from this, expressing the idea of walking or behaving arrogantly or self-importantly. By the late 18th century the ‘bulging bag’ meaning of swag had come to be applied to a thief’s booty. It also came to refer to a bundle of personal belongings carried by a traveller in the Australian bush [M19th], hence the ‘jolly swagman’ of Waltzing Matilda.