| 1 | Irish | aisteach | peculiar, queer, strange, unusual; wonderful,... |
| 2 | Irish | aiste | quirk, peculiarity; knack; odd talent; manner,... |
| 3 | Old Irish | aiste | characteristic, special quality, peculiarity;... |
| 4 | Latin | essentia | essence, being |
| 5 | Latin | esse | present infinitive of sum; state, condition;... |
| 6 | Ancient Greek | οὐσία | that which is one's own, one's substance,... |
| 7 | Ancient Greek | εἰμί | To be, exist; live; To be; it is possible |
| 8 | Proto-Hellenic | ehmi | to be |
| 9 | Proto-Indo-European | h₁ésmi | first-person singular present indicative of... |
| 10 | Proto-Indo-European | h₁ēs- | — |