Consider this - from the COED
RoverConcise Oxford English Dictionary © 2008 Oxford University Press:
▶pronoun [third person sing.]informal used instead of ‘himself’ or ‘herself’ to refer to a person of unspecified sex.
usage: The standard reflexive form corresponding to they and them is themselves. The singular form themself has been used recently to correspond to the singular use ofthey when referring to a person of unspecified sex, as in helping someone to help themself. However, themself is not regarded as good English, and themselvesshould be used instead. For more details, see usage at they.
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