That's what C.P. Baker calls him in his Tiberius Caesar, Emperor of Rome, in the chapter "The Advent of the Tuscan," p. 221 ff. Online
[…] He was a Tuscan, sprung of that strange, dark and
ancient Etrurian race which seemed to derive many of
its typical characteristics from an older culture than
that of classical Greece and Rome. The Etrurian possessed a start in the virtues and vices of civilization that
the Roman, trained in a later school, never quite recaptured: his very mind and temperament, like those of
the Jew, were attuned by a remote historical experience
to the life of populous cities and crowded human society.
Maecenas had been a Tuscan—that very wise man of
the world who never fought nor worked, but, because
he lived in a torrent of talk, ruled the men who did so.
. . . After all, the art of arriving at an understanding
with other men is the whole art of civilization.
Seianus possessed this gift. He had a genius for adapting himself to other men. We may call it genius, for
he successfully adapted himself to the mind of one of
the subtlest, most discerning, and most difficult men
who ever lived Tiberius.
Seianus stood to Tiberius in a relation not altogether unlike that in which the latter had stood to Augustus. But there were differences worth noting. . . . Seianus had not quite given Tiberius those guarantees of fidelity which the latter had given to Augustus. He had never humbly subordinated himself, nor served those years of self-repression which Tiberius had served: he had never retired to Rhodes, nor disinherited his own son for such adopted heirs as Germanicus and Agrippina. A man grows cold with age: and the older Tiberius grew, the less he was likely to relish the strain of lusciousness that marked the Tuscan. Seianus had bloomed with some of the quality of a tropical orchid. He was a man who did not know how to lose himself in his background.
All in all, Baker's assessment of Tiberius and Sejanus stacks up very well against the more recent biographies by professional historians such as Levik and Seager – although he buys the Apicata story that Drusus was murdered by Sejanus and Livilla – and it reminds me again how much I like Baker's writings, his eclectic prose notwithstanding. His descripition of Sejanus final fall in the Senate session is riveting (p. 260 ff).
