Caligula’s command to gather seashells likely reflected confusion over siege engine terminology.

Evidence

It is, for example, possible that Suetonius’ sea-shells (conchae) originate from a military technical term for ‘mobile shelters used in siege-assaults’ (musculi), which is also the word for ‘mussels’. Hence, perhaps, the order to ‘Pick up the musculi!’ gets distorted to ‘Pick up the conchae!’ — Stephen Kershaw, A Brief History of the Roman Empire, 481

Categorization

• corroborated: 2 independent passages support this claim — Stephen Kershaw, A Brief History of the Roman Empire, 481