'mainland-born' is a compound of 'mainland' + 'born'. 'mainland' originates from Middle English (a combination of 'main', meaning 'principal', and 'land'). 'born' comes from Old English past-participle forms of the verb 'to bear' (Old English 'beran').

'mainland' was formed in Middle English from the elements 'main' (principal) + 'land'. 'born' comes from Old English past-participle forms such as 'geboren'/'boren' (from the verb meaning 'to bear'), and developed into modern English 'born'. The compound 'mainland-born' is a more recent formation combining these elements to describe place of birth.

The parts originally referred separately to 'principal land' (mainland) and the past participle 'born' (originating from 'to bear'). Over time the compound came to be used adjectivally to indicate a person's place of birth: 'born on the mainland.'