The day is named in honor of the righteous martyr Theodulus of Thessalonica, a church reader from Thessalonica, revered on this date among Orthodox believers. The winds became warm among the people from Fedula Vetrenik, which is why the day was called that. On the day of Fedul Vetrenik there was a custom to ventilate the room. After a long winter, this was useful, and the air outside was warm and did not freeze the rooms.