The term "null" comes from C. A. R. Hoare, who has proposed in November 1965 various additions to the programming language ALGOL 60, including pointers (called references by Hoare, "pointer" comes from IBM PL/I, in July 1966), and including a special value "null" for references a.k.a. pointers, for denoting unknown or not applicable values.
C. A. R. Hoare, 1965-11:
"In order to enable references to represent partial functional relationships, i.e. ones which do not necessarily yield a value, a special reference value null is introduced.
This value fails to refer to a record, and any attempt to use it to refer to a record leads to an undefined result."
In his proposal, Hoare has followed the COBOL 60 terminology for some of the additions to ALGOL, i.e. "record" instead of the word "structure", introduced by IBM PL/I in 1964-12, and "record class" instead of "structure type", hence the "class" of SIMULA 67, from where the word "class" has spread into all OOP languages.
In Hoare's proposal, references a.k.a. pointers could point only to values belonging to user-defined types, i.e. records a.k.a. structures, not to primitive types.
C. A. R. Hoare, 1965-11:
"In order to enable references to represent partial functional relationships, i.e. ones which do not necessarily yield a value, a special reference value null is introduced. This value fails to refer to a record, and any attempt to use it to refer to a record leads to an undefined result."
In his proposal, Hoare has followed the COBOL 60 terminology for some of the additions to ALGOL, i.e. "record" instead of the word "structure", introduced by IBM PL/I in 1964-12, and "record class" instead of "structure type", hence the "class" of SIMULA 67, from where the word "class" has spread into all OOP languages.
In Hoare's proposal, references a.k.a. pointers could point only to values belonging to user-defined types, i.e. records a.k.a. structures, not to primitive types.