The story
From the Lakota word thípi (/ˈtʰipi/), which consists of two elements: the verb thí (“to dwell”), and pi, a pluralising enclitic (a suffix-like ending that marks the subject of the verb as plural), which means they dwell. Lakota verbs can be used as nouns and this is the case with thípi, which in practice simply means house.
Etymology from Wiktionary, CC BY-SA 4.0.