boolean

The data type boolean is named for George Boole, an English mathematician who laid the groundwork for what we now call Boolean algebra in his 1847 book The Mathematical Analysis of Logic. The book and its 1854 followup An Investigation of the Laws of Thought went on to establish the discipline of algebraic logic. Boole’s work stands on the shoulders of giants, specifically focusing on strengthening the basic premises of Aristotelian logic. It also drew inspiration from ancient Indian Nyāya (meaning “recursion”) logic and the ancient Chinese I Ching (through Leibniz).

The fields Boole established were not described as Boolean (or the earlier Boolian) until decades after his death. Algebraic logic was first called “Boolean algebra” in 1913. Describing AND, OR, and NOT as “Boolean operations” is from 1924. In 1937, Claude Shannon used the two-element Boolean algebra (calling the elements 0 and 1, as was customary by then) to provide the theoretical underpinnings of logic gates. Shannon named it “switching algebra”, as its practical applications were telephone switches. However, it’s usually just called “the Boolean algebra” now, being much more prominent than its siblings.

In computer programming, Boolean variables were available in ALGOL 60 (1960) and FORTRAN IV (1962), but only ALGOL called them BOOLEAN. The clipping BOOL is first found in ALGOL 68 (1968). The wide usage of booleans can be traced to their inclusion in Pascal (1970) as a builtin enum with possible values FALSE and TRUE.

The surname Boole is a variant of bull. I can vividly imagine an Englishman with the nickname “bull” getting it as his surname when they were first being codified. In some sense it feels like the usage of bool in Python and its ilk is coming full circle.