Green’s Dictionary of Slang

1. (bingo) the number six or 66.

1917		A.G. Empey Over the Top 148: The caller-out has many nicknames for the numbers such as [...] ‘Clickety-click’ for sixty-six.
1925		(con. WWI) Fraser & Gibbons Soldier and Sailor Words 58: Clickety Click: 66 in the game of ‘House’.
1936		(con. 1900s) F. Richards Old Soldier Sahib (1965) 71: No. 66 – Clickety-click.
1947		J. Maclaren-Ross Of Love And Hunger 116: Dead-pan geezer in a white coat calling the numbers. 90, top of the House. 66, clickety-click.
1962		K. Waterhouse There is a Happy Land (1964) 87: Clickety-click, sixty-six.
1972		(con. 1940s) N. Conway Bloods 115: The caller had sung out his litany of Legs Eleven, Kelly’s Eye, Knock on the Door, Clickety-Clicks.
1980		T. McClenaghan Submariners I ii: Sixty-six clickety click. Four and five half way.
2003		Observer 6 July 16: Old favourites such as [...] ‘clickety click’, 66.

2. (Aus.) a stick.

2002

Pete’s Aussie Sl. Home Page 🌐 clickety-click: a stick.