Green’s Dictionary of Slang

(Aus.) a utility vehicle.

1957		R.S. Porteous Brigalow 26: They rarely showed fear of us, even when Carson careered round a mob in the rattling tilly.
1960		R.S. Porteous Cattleman 228: He’s driving down in the tilly and he’ll be here between eight and nine.
1977		V. Priddle Larry & Jack 14: ‘What makes you walk out here in this heat, George? What’s wrong with the old “Tilly”?’ ‘I never drive the old bus when I know I’m going to have a few grogs.’ [AND].
1993		Aus. Word Map 🌐 tilly utility or ute: let’s load the tilly and get to work.