'invitation-only' is a compound adjective formed from 'invitation' and 'only'. 'Invitation' originates from Latin 'invitatio', meaning 'a calling or summoning'.

'Invitation' evolved from the Latin 'invitatio' through Old French 'invitation', and 'only' has remained largely unchanged from Old English 'anlic'.

Initially, 'invitation' meant 'a calling or summoning', and 'only' meant 'solely'. Together, they now mean 'restricted to those invited'.