What does T-VEC stand for?
The name T-VEC is short for Test VECtor.
The original tool T-VEC was created in 1988, and the term test vector was used to represent a set of input values and corresponding expected output values produced by T-VEC (now the VGS component of T-VEC). A test vector represents a line from a point in the input space to a point in the output space of the system boundary that are to be tested. The term was used in the digital hardware domain where the use of "test vector" may have been associated with a 1 dimensional array of input values to the digital circuit being tested - and in linear algebra a 1 dimensional array is called a "vector." The perspective from the original concept in T-VEC comes from a geometric definition of vector, a line between 2 points with a direction associated with it (i.e., from input to output). This may have been the first use of the term "test vector" in software testing domain, and it was used to distinguish "test vectors" from "test cases," which was more generally associated with test inputs only, because T-VEC generates not only input value sets but expected output values from model information.
Coincidently around the time when T-VEC was being used in its first FAA certification, DO-178B was in the works and there was a movement from white-box based testing of DO-178A to requirements based testing of DO-178B. Members of the committee were familiar with T-VEC and the term "test vector" was in use, and the industry seems to have adopted this term too.