Bhagavad Gita, Chapter 17, Verse 25

Uttering Tat, without aiming at fruits, are the various acts of Yajna, austerity and gift performed by the seekers of Moksha.

A second real word is named here specifically for those seeking freedom rather than reward.

Krishna ties this particular syllable to a real, specific intention, detachment from results. The word itself is shown carrying that meaning into the practice.