'MP' originates from English, specifically the phrase 'Member of Parliament'.

'Member of Parliament' developed from the combination of 'member' (one belonging to a body) and 'parliament' (a legislative assembly); the initialism 'MP' arose later as a convenient shortening in modern English and the plural form 'MPs' follows normal English pluralization.

Initially it referred to an individual who belonged to a parliament; over time the abbreviated forms 'MP' and 'MPs' have been used widely in speech and writing to mean the same thing.