Green’s Dictionary of Slang

1. an imaginary or unknown person; see cit. 1860.

1845		J. Lindridge Sixteen-String Jack 206: Singing ran diddle, Oh! Snooks vos the man, / With his quips and cranks so leary.
1860		Hotten Dict. of Modern Sl. etc. (2nd edn) 221: snooks an imaginary person often brought forward as the answer to an idle question, or as the perpetrator of a senseless joke.
1864, 1867, 1870		Hotten Sl. Dict.
1868		Louisville Dly Courier (KY) 22 Mar. 1/8: Snook’s opinion is a matter of small importance to the world outside his own fireside [...] All the great family of Snookses [...] your igorance would excite pity if your arrogance were less exasperating.
1880		W. Hooe Sharping London 36: Snooks, an imaginary third person.
1900–10		Stephens & O’Brien Materials for a Dict. of Aus. Sl. [unpub. ms.] 144: SNOOKS THE BOTTLE WASHER: a mythical person; an epithet applied to an unknown person.
1919		‘Sapper’ Mufti 78: If you prefer it — may I ask your age, Miss Snooks?
1922		‘Sapper’ Black Gang 403: I’ve forgotten under what name you inflict yourself on a long-suffering world, but I shall call you Snooks.

2. (also snook, snookie) a term of endearment, either to a child or lover.

1916		Winnipeg Trib. (Manitoba) 9 Dec. 48/1: ‘I’ve been looking for you everywhere, Snooks,’ he said.
1984		Partridge DSUE (8th edn) 1105/1: since ca. 1925.
1997–2000		College Sl. Research Project (Cal. State Poly. Uni., Pomona) 🌐 Snook (snookie) (voc.) A term of endearment one uses in direct reference to one’s close friends.