Green’s Dictionary of Slang

(S.Afr.) the buttocks, the posterior; thus come on one’s guava, to make a fool of oneself.

1975		‘Blossom’ in Darling 95: This oke sticks he’s foot out [...] so I trip over it and end up on my guava [DSAE].
1996		CyberBraai Lex. at www.matriots.com 🌐 In South Africa a guava is also a backside, a butt, a bum. If someone is behaving in an annoying manner, you can threaten to ‘skop (kick) him up his guava’.