What is the origin of the idiom "sharp as a tack" and when to use it?

The phrase "sharp as a tack" is believed to have originated in the United States, likely in the early to mid-20th century. The phrase draws upon the sharpness of a tack, which is a small pointed nail used for securing objects. This idiom is used to emphasize someone's intelligence, mental acuity, and quick thinking. It conveys a sense of admiration for their sharpness of mind and intellectual prowess.