untrustworthiest

And the ladies and gentlemen who are so very anxious to know the orthography of certain words! How often am I to repeat that I never learned to spell, that I am unacquainted with the laws of English spelling, and that I am consequently the untrustworthiest of guides on the matter of orthography.

1884 July 12, G. A. S., “Echoes of the Week”, in The Illustrated London News, volume LXXXV, number 2360, London, page 27, column 3

The Tiriotes, from ancient custom, wear large linen cloths, slung around their ugly heads, in the form of a turban, in order to have the appearance of an “Adamy,” a quiet, good man. But in reality they are the greatest thieves, the untrustworthiest crowd around, and are known as such everywhere.

1887, G. Schumacher, “Arabic Proverbs. Used to characterize some villages in the District of Akka.”, in Palestine Exploration Fund. Patron—The Queen. Quarterly Statement for 1887., London: Society’s Office, […], and by Richard Bentley & Son, […], page 193

“Oh, I don’t know, my lad. Sometimes, and sometimes there's fair breezes. But lor’ bless you, it’s the same everywhere. Weather’s about the untrustworthiest thing I know.”

1900, Farmer’s Advocate and Home Magazine, volume 35, page 237, column 3

Why did George Sand exercise such a spell over men of genius? Was she ever quite in earnest except when she said to Sainte-Beuve, untrustworthiest of confidants, yet quaintly popular in that capacity: “I have never met the being with whom I could live and die; and if I could, I should not know how to keep him”?

1911, The Lady’s Realm: An Illustrated Monthly Magazine, volume 29, page 472, column 1

"I was born at night, second and third / Of January in that untrustworthiest of years / 'Ninety-something-or-other and the centuries / Compass me with fire."

1979, For John Riley, Grosseteste Press, page 31