o dan

• dan

From Middle Welsh a dan, from Old Welsh guotan. Reanalyzed in modern Welsh as o (“of, from”) +‎ tan (“under”), but the first element is not actually o (“from”), but instead it was in reality Proto-Celtic *uɸo (“under”), which outside of o dan went extinct in Brittonic as a free-standing preposition.^[1]

• IPA^(key): /ɔˈdan/

o dan (triggers soft mutation on a following noun)

1. under

   Synonym: islaw

In literary Welsh, tan can mean both "under" and "until". In Welsh usage today, however, dan (originally the soft mutation of tan) has become a preposition in its own right with the meaning "under" whereas tan means "until", retaining the meaning "under" in certain expressions, compound words and place names. Modern dan or tan are not usually mutated. o dan is an alternative to dan.