Green’s Dictionary of Slang

(UK Und.) admirably, excellently; in pleasant circumstances.

1865		Leaves from Diary of Celebrated Burglar 42/2: He was told to make himself at home. This he did by ‘turning up’ the ‘moll’ that brought him there, an fixing himself ‘ryebuck’ with Selina.
1904		Sydney Sportsman (Surry Hills, NSW) 14 Dec. 3/4: First: How yer gettln’ on with old Golddust’s daughter? Second: Ribuck! Wish the ole man was as easy to get round as the daughter.