tathāgata

The Buddha – “thus gone” – “arrived at suchness (reality beyond definition)” – “thus in being”

tatha – truth; reality; being
gata – gone; rooted in

https://en.wikipedia.org/wiki/Tath%C4%81gata
https://buddhism.stackexchange.com/questions/1629/why-does-the-buddha-call-himself-the-tath%c4%81gata