From two sources, both reflecting earlier *-ōjaną:
- From Proto-Indo-European *-eh₂yéti, an innovated compound suffix from *-eh₂ (eh₂-stem noun suffix) + *-yéti (denominative suffix). These were originally formed as denominative verbs from ō-stem nouns. When attached to thematic (a-stem) nouns, the thematic vowel was also retained, but the resulting compound suffix *-eyé- became part of the first weak class instead.
- From Proto-Indo-European *-(e)h₂yéti, an innovated compound suffix from *-(e)h₂ti (factitive verb suffix) which was originally athematic, but later extended with the thematic present suffix *-yéti.
|active voice||passive voice|
This class eventually became the dominant and most productive verb class in all daughter languages. In northern West Germanic, the suffix was reanalysed and extended to -ōjaną based on the first and third class of weak verbs.
- Old English: -ian
- Old Frisian: -ia
- Old Saxon: -ōn, -oian
- Old Dutch: -on
- Old High German: -ōn
- Old Norse: -a
- Gothic: -𐍉𐌽 (-ōn)