These names essentially come from the PDP-10 which has instructions for all 16 boolean operations: 0000 SETZ 0001 AND 0010 ANDCA 0011 SETM

These names essentially come from the PDP-10 which has instructions for all 16 boolean operations: 0000 SETZ 0001 AND 0010 ANDCA 0011 SETM 0100 ANDCM 0101 SETA 0110 XOR 0111 IOR 1000 ANDCB 1001 EQV 1010 SETCA 1011 ORCA 1100 SETCM 1101 ORCM 1110 ORCB 1111 SETO Where A = accumulator, M = memory, B = both, C = complement of, Z = zero, O = one. The LISP machine processors (CONS, CADR) also had a 74181 ALU which you could control directly so these names were used again on that platform.