themself

Etymology

From Middle English theimself. Equivalent to them + -self. Reinforced by analogy with the singular-plural distinction between yourself and yourselves.

pron

1. (reflexive) The reflexive form of they, the third-person singular personal pronoun. The single person previously mentioned, as the object of a verb or following a preposition (also used for emphasis).
   Someone could hurt themself.
   Anyone who wants a car like mine can buy one themself.
   ... they woulden't always be trying to make Themself Look Diffarunt... December 6, 1899, “Paw Baldness”, in Shiner Gazette
   THE author who masqueraded as Helen Demidenko yesterday urged the hoaxer who deceived the respected right-wing journal Quadrant to unmask themself. January 8, 2009, Samantha Maiden, “Hoaxer, out yourself: 'Demidenko'”, in The Australian
   ... somedays there will be an odd number of quadders and so somebody might have to sit by themself in the back. January 8, 2013, John Stoltenberg, Gonerz
2. (nonstandard, sometimes proscribed) Synonym of themselves (the third-person plural).
   […] and the same is here thought of al men to be so vailable and sufficient, as can be required, accept and take the said commission and dispensation so thankfully, and themself so satisfied with the same, that they repute and think themself not only singularly obstringed and bound to the Popes […] 1822, John Strype, Ecclesiastical Memorials, Relating Chiefly to Religion, page 119