'firmly-attached' originates from the combination of 'firmly' and 'attached', where 'firmly' is derived from the Old English 'fyrm' meaning 'strong' and 'attached' from the Old French 'atachier' meaning 'to fasten'.

'firmly-attached' evolved from the Middle English 'firmly' and 'atachier', eventually becoming the modern English term 'firmly-attached'.

Initially, it meant 'securely fastened', and this meaning has largely remained the same in modern usage.