Why is "Tathāgata" not "One Who Is Thus"?

[Sphairos]

Yes, that’s what it most likely means.

See also here :

“Tathagata” - Phonology

Regarding the pronunciation of tathāgata, see this recording of the recitation of the First Sermon (Thai style): [บทสวดมนต์ ธัมมจักกัปปวัตตนสูตร - Dhammacakkappavattana Sutta - 转法轮经 17 นาที l Sub TH + Eng + Ch] Regarding the meaning, see this old paper by E. J. Thomas: https://www.jstor.org/stable/608088 Where he points out that in Jaina Āgamas, there is an Ardha-Māgadhī term tahāgaya, which is an epithet of the Mahāvīra, meaning something like “one who has reached seeing/knowi…