'firmly-linked' originates from the combination of 'firmly,' meaning 'in a strong, secure manner,' and 'linked,' meaning 'connected or joined.'

'firmly' comes from Old English 'fyrmlice,' and 'linked' comes from Middle English 'linken,' both evolving into the modern English usage.

Initially, 'firmly' meant 'securely' and 'linked' meant 'connected,' and these meanings have largely remained the same in modern usage.