Green’s Dictionary of Slang

1. phr. denoting speed and repetition.

1843		Satirist & Sporting Chron. (Sydney) 4 Mar. 2/2: The person [...] who had been observed [...] ‘going in and out like a fiddler’s elbow, or a dog in a fair’ [...] about the counting house .
c.1951		N. Algren ‘Watch Out for Daddy’ in Entrapment (2009) 149: I’m in and out of jail like a fiddler’s elbow.

2. (Aus., also in and out like a dog pissing in the snow) all over the place, in terms of useless over-activity.

1948		P. Kavanagh Tarry Flynn (1965) 31: As he was using only one horse to pull the plough the work was rather bumpy – and in the local phrase ‘in and out like a dog pissing in the snow’.
1982		N. Keesing Lily on the Dustbin 186: Two examples are ‘in and out like a fiddler’s elbow’ or ‘rushing around like a one-armed fiddler with the itch’ whose innocuous meanings merely describe useless or senseless over-activity.
1995		P. O’Keeffe Down Cobbled Streets, A Liberties Childhood 134: What ails you? [...] You’re in and out of here like a fiddler’s elbow.

3. rapid and enthusiastic copulation.

[1793		Bacchanalian Mag. 98: Original and selected Toasts and Sentiments [...] The quintessence of Love — A shake like a fiddler’s elbow, and a squirt like a fire engine].
1985		R.G. Barrett You Wouldn’t Be Dead for Quids (1989) 68: Sophia straddled him [...] It wasn’t long before her backside waas going up and down like a fiddler’s elbow.
1986		R.G. Barrett Godson 110: [H]is behind was going up and down like Yehudi Menuhin’s elbow.
2000–2002		Kayel ‘Sexual Thesaurus’ at FreePornForWomen.com 🌐 In and out like a fiddler’s elbow Having sex quickly.