The nominative singular lacks the final consonant of the stem. This preserves an old sound change from late PIE, where word-final -t becomes -d. According to Grimm's law, t shifted to þ, and d shifted to t. Following this, word-final -t was lost regularly.
- Old English: ealu
- Old Saxon: alo
- Old Dutch: *alo
- Old Norse ǫl
- → Proto-Finnic: *olut (possibly)
- Latvian: alus (possibly)
- → Ossetian: ӕлутон (æluton) (possibly)