Definition of "wunst"

"Mrs Harris," I says to her, "none on us knows what we can do till we tries; and wunst, when me and Gamp kept 'ouse, I thought so too.

1842–44, Charles Dickens, Life And Adventures Of Martin Chuzzlewit‎

Wouldn't they let him and Sam off this wunst?

1866, George Alfred Townsend, Campaigns of a Non-Combatant,‎

"If it was just for wunst," she had begun, when Tishy tweaked her sleeve viciously and interpolated a rapid whisper, "It wont be; there'll be no ind to it if you begin humourin' them," so the sentence was badly dislocated.

1895, Barlow Jane, Strangers at Lisconnel‎

By way of an incident: a pair of these primitives were overheard chatting about the resorters, one day, and in the course of their talk this remark was dropped: "I was a-drivin' a passel of 'em round about yisterday evenin', quiet ones, you know, still and solemn, and all to wunst they busted out to make your hair lift and I judged hell was to pay.

1906, Mark Twain, Chapters from My Autobiography‎

"Skim, you 'member in thet las' book we read, 'The Angel Maniac's Revenge,' there was a sayin' that fate knocks wunst on ev'ry man's door.

1908, Edith Van Dyne, Aunt Jane's Nieces at Millville‎

"Well, ma'am," remarked the Cap'n, dryly, as he seated himself in another chair, "I've waded across a cove wunst or twice at low water."

1911, Holman Day, The Skipper and the Skipped‎