| Common name | Siwin |
| Language | Welsh |
| Type | Vernacular |
| Official trade name | No |
| Rank | 2 - (Preferred common name (unique)) |
| Country | England and Wales (UK) |
| Locality | |
| Ref. | Wheeler, A., 1992 |
| Life stage | juveniles and adults |
| Sex | females and males |
| Core | |
| 1st modifier | |
| 2nd modifier | |
| Remarks | Adapted as 'sewin' in English for the sea trout which is of considerable angling importance in Wales. |