Bordeaux: They are neither generous nor vigorous, but the bouquet isn’t bad, and they have an indescribably sinister, sombre bite that is not at all disagreeable. – Alexandre Dumas, quoting Cardinal Richelieu
Fascinating article by Tim James who, after Eben Sadie stated he intended to make his Columella more sinister, uncovers the origin of 'sinister'.
As the linked article points out "sinister" is an inadequate translation for "sournois" but I find it impossible to propose a one word alternative which would catch the essence of what Richelieu was saying. The conventional translations like "furtive", "underhand" or "devious" would not fit the bill. Another example of "traduttore, traditore"?