The phrase “keeping him on his toes” means to keep someone alert, vigilant, or attentive, often by presenting challenges or surprises that require them to be ready to respond or adapt. It suggests that the person cannot become complacent or relaxed because they are continuously faced with new situations or demands that require their focus and quick thinking.
This expression can be used in various contexts, such as in a workplace setting where a manager might keep employees on their toes by introducing new projects or changes, or in personal relationships where one person may challenge the other to try new activities or stay engaged.
Overall, the idea is to maintain a sense of dynamism and engagement, preventing stagnation or boredom.