PIE base ‘to swell’.
Derivatives include butter, tumour, thumb, tumult, tuberculosis, thousand (swollen hundred), and autosoteria, through Greek saos, sōs ‘safe, healthy’, in sense something that is swollen is strong, giving sōzein ‘to save’.
[Pokorny tēu-, təu-, teu̯ə-, tu̯ō-, tū̆-, pp. 1080–1085.]
Glossary terms for this common ancestor to be added.