the.com/foursquare

means Solidly and openly direct or forthright — and literally, having four equal sides set squarely, like a building planted firmly on its foundation.

from From 'four' plus 'square,' originally a plain architectural term for something built with four equal sides set at right angles — a shape as stable as it sounds. By the 1300s English speakers had already stretched it metaphorically: a person could be 'foursquare' too, meaning firmly and uncompromisingly planted in their opinions, as solid-footed in argument as a well-built structure. The app borrowed that old sturdiness and pointed it at your location instead of your character.