Green’s Dictionary of Slang

one’s special choice, e.g. a glass of my particular.

1809		A.B. Lindsley Yankee Notions 8: We stopt at New York, and took in a few barrels of old Newark ’ticular.
1826		C.M. Westmacott Eng. Spy II 311: I will engage to give you a hearty welcome, and another bottle of the old particular.
1849		Bell’s Life in Sydney 3 Feb. 3/2: He would take the smaller sum, and a few glasses of his ‘particular,’ as an acknowledgment, of his ben- evolence.
1912		Bulletin (Sydney) 12 Dec. 34/2: ‘A drop of my particular, Fred,’ he said, rather queerly, and still with emotion.