From Wiktionary, the free dictionary
Corruption of Malay buah duku (“fruit of the tree Lansium domesticum, langsat”).
baluku
- (colloquial, Singapore) A swollen bruise or bump on the head; a goose egg.
2018, Jean Tay, Sisters & Senang: The Island Plays, Epigram Books, →ISBN, Scene 12, page 73:My head hit the windscreen, so baluku lor.