err on the side of something
err on the side of (something)
To prioritize something, perhaps excessively or unnecessarily. Often used in the phrase "err on the side of caution." I like to err on the side of caution and always keep some money in my savings account.
err on the side of somethingshow slightly too much rather than too little of a quality, especially a good one: When I am marking exam papers, I always try to err on the side of generosity (= I give slightly higher marks than the students may deserve).
Err is an old-fashioned word meaning ‘make a mistake’.