have one’s wits about one, to

To be wide awake and alert. Wits in the plural has long meant keen mental faculties. Ben Jonson so used it in The Alchemist (1612): “They live by their wits.” About the same time, the expression of having one’s wits about one—in effect, ready to serve one— came into use. It appeared in James Mabbe’s 1622 translation of Guzman de Alfarache (“I had my wits about me”) and has been used ever since. To live by one’s wits, on the other hand, also implies managing by means of clever expediency rather than honest work.