elĉerpiĝi

Three pieces, and taking them apart teaches the word. Ĉerpi is to draw water from a well with a bucket. El- is out. So elĉerpi is to draw it out until the well is dry - to use something up completely. Then -iĝ- turns the transitive verb round: instead of somebody exhausting the supply, the supply exhausts itself.

That is the whole -ig- / -iĝ- contrast in one word. Elĉerpi la monon is to spend it all; la mono elĉerpiĝis is the money running out with nobody named as the culprit. English uses two unrelated phrasings for that pair - "use up" and "run out" - where Esperanto changes one letter. How -ig- and -iĝ- work is the article to read if the pattern is still slippery.

It covers people as well as supplies. Mi elĉerpiĝis means I am shattered, and elĉerpita does duty for both a wrung-out person and a sold-out concert. Watch the two hats: ĉ is the ch of church, ĝ the j of judge, so the whole word runs el-CHER-pee-jee in the infinitive.