Green’s Dictionary of Slang

balls-up n.

also balls
[synon. with cock-up n.; fuck-up n. (1)]

1. [late 19C+] (orig. milit.) a blunder, an error.

2. attrib. use of sense 1.

In phrases

make a balls of (v.)

[late 19C+] to make a mistake, to get into trouble.

make a barney balls of oneself (v.)

[1940s+] (Irish) to make a fool of oneself.