Etimology
Morphologically them + -selves.
pronoun
themselves (third-person, reflexive of they)
(reflexive) The reflexive case of they, the third-person plural personal pronoun. The group of people, animals, or objects previously mentioned, as the object of a verb or following a preposition (also used for emphasis).
(reflexive) The reflexive case 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).
Examples
: They’ve hurt themselves.
: They fought among themselves.
: They are going to try climbing Mount Everest themselves.
The preposterous altruism too! […] Resist not evil. It is an insane immolation of self—as bad intrinsically as fakirs stabbing themselves or anchorites warping their spines in caves scarcely large enough for a fair-sized dog.
: Would whoever stole my phone please make themselves known.
: I don't want anyone to fight among themselves.
: Everyone must do it themselves.
Let nothing be done through strife or vainglory; but in lowliness of mind let each esteem other better than themselves.
In fact she was so busy doing all the things that anyone might, who finds themselves alone in an empty house, that she did not notice at first when it began to turn dusk and the rooms to grow dim.
Related words
synonyms
'emselves (colloquial)
theirselves (nonstandard)
(singular): themself (non-gender-specific), theirself (non-gender-specific, but nonstandard), himself, herself (gender-specific)