'rapidly-gained' originates from the combination of 'rapidly,' meaning 'quickly,' and 'gained,' meaning 'acquired or obtained.'

'Rapidly' comes from the Latin word 'rapidus,' meaning 'swift,' and 'gained' comes from the Old French 'gaigner,' meaning 'to earn or win.'

Initially, 'rapidly' meant 'swiftly' and 'gained' meant 'earned or won,' and together they convey the idea of something acquired quickly.