Green’s Dictionary of Slang

cargo n.1

[ety. unknown. Despite the apparent logic of relating this to cargo n.2 , i.e. a person as a fig. burden or load, this use precedes the adoption of the Sp. word into SE, and there is no evidence of Sp. cargo being used in this way]

a person.

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[UK]Jonson Poetaster V i: What! will the royal Augustus cast away a gentleman of worship, a captain and a commander, for a couple of condemn’d caitiff calumnious cargos.