In the text Linear Algebra (by Hoffman and Kunze), there are notations S, Z, M. What are these short for – that is, why are these particular three letters used for the following concepts?
(i) S. Let $W$ be an invariant subspace for $T$ and let $\alpha$ be a vector in $V$. The $T$- conductor of $\alpha$ into $W$ is the set $S_{T}(\alpha ; W)$, which consists of all polynomials $g$ (over the scalar field) such that $g(T)\alpha$ is in $W$.
(ii) Z. If $\alpha$ is any vector in $V$, the $T$- cyclic subspace generated by $\alpha$ is the subspace $Z(\alpha ;T)$ of all vectors of the form $g(T)\alpha$, $g$ in $F[x]$.
(iii) M. If $\alpha$ is any vector in $V$, the $T$-annihilator of $\alpha$ is the ideal $M(\alpha ; T)$ in $F[x]$ consisting of all polynomials $g$ over $F$ such that $g(T)\alpha = 0$.