Green’s Dictionary of Slang

(Aus.) stones used to form a roadway; usu. in context of being thrown by a young criminal.

[1847		[A. Harris] (con. 1820s) Settlers & Convicts 159: He did not object to stow himself [...] under the ‘gibbers’ (overhanging rocks)].
1880		Bulletin (Sydney) 25 Dec. 3/4: An able-bodied corporation labourer [...] was carefully picking up loose bits of road-metal [...] he afterwards spent half a day wiping the ‘gibbers’ with his handkerchief.
1894		‘The Rocks Push Eisteddfod’ in Bird o’ Freedom (Sydney) in J. Murray Larrikins (1973) 89: They slottie gibber in my shlop, / They punch me in der head!
1904		Sydney Sportsman (Surry Hills, NSW) 20 Apr. 2/7: [headline] Ex-Rev George Saw Ghostly Gibber Slingers.
1951		Mail (Adelaide) 1 Dec. 2s/5: Australians have bult up a vocabulary of some 7,000 slang words [...] gibber (stone).
1973		(ref. to 1890s) ‘Gloss. of Larrikin Terms’ in J. Murray Larrikins 202: gibber, ghibbers: stones, blue metal, especially for throwing.
1993		Aus. Word Map 🌐 gibber n. a stone or pebble.