Wurdahuzdą: Proto-Germanic dictionary

noun masculine an-stem like modern English “-er”; forms masculine agent nouns and personal nouns, often from the zero-grade of the base From Early Germanic *-jan-/*-jōn-, the weak masculine counterpart of agentive and personal nouns in *‑ja-/*-jō-. The formation combines a *j-element, probably related to the Proto-Indo-European relational or appurtenance suffix *-yo-, with the inherited individualizing n-stem inflection. The exact chronology of the combination is uncertain: some formations may continue inherited complex suffixes, while others may have arisen within Germanic through the transfer of ja-stems to the productive weak declension Kroonen 2011a: 64–65 Lehmann 1986a: §4.2.2 Pronk 2015: 327–29. Declension

The suffix varies as *-jô/*-ijô based on Siever’s Law: the basic *-jô form is used after a “light” syllable (a short vowel followed by a single consonant), and otherwise, the form becomes *-ijô.