| 1 | English | orthogonal | Of two objects, at right angles; perpendicular to... |
| 2 | Middle French | orthogonal | — |
| 3 | Medieval Latin | orthogonalis | orthogonal |
| 4 | Latin | orthogonius | right-angled; rectangular; orthogonal |
| 5 | Ancient Greek | ὀρθογώνιος | right-angled; rectangular |
| 6 | Ancient Greek | ὀρθός | straight, upright, erect; straight forward, in a... |
| 7 | Proto-Hellenic | ortʰwós | — |
| 8 | Proto-Indo-European | h₃r̥dʰwós | — |
| 9 | Proto-Indo-European | h₃erdʰ- | to increase, grow; upright, high |
| 10 | Proto-Indo-European | -wós | Creates adjectives from verb stems |