The indefinite pronouns of a language, like the English terms "somebody" and "something," are derived from its interrogative pronouns, as in the English "who" and "what."  Consider Russian, where the indefinite suffix <i>-to</i> is used to derive the indefinite pronouns <i>kto-to</i> 'somebody' and <i>Äto-to</i> 'something' from the interrogatives <i>kto</i> 'who' and <i>Äto</i> 'what.'

<br><br><b>Reference</b><br>
Haspelmath, Martin. 2008. Indefinite Pronouns.
In Haspelmath et al (2008), chapter 46. Available online at <a href="http://wals.info/feature/46">
http://wals.info/feature/46</a href>.
