As I learned french earlier I remember the french forms but they are all derived from Latin: lundi = dydd llun (moon day), mardi = dydd mawrth (mars day), mercredi = dydd Mercher (Mercury day).
but french doesn’t work so well for jeudi = dydd Iau (Jupiter day), vendredi = dydd Gwener (Venus day), samedi = dydd Sadwrn (Saturn day), dimanche = dydd Sul (Sun day).
I also remember ddyd Mercher as market day (thinking merchant and, of course, marchnad) as that was the tradition (Wednedsay markets - marchnad y ffermwyr bob dydd Mercher) in many places. Nice that it’s mnemonic.
Indeed they do.
dydd "day" is native, but the day names are borrowed from Latin:
- dydd Llun from dies Lunae "day of the Moon"
- dydd Mawrth from dies Martis "day of Mars"
- dydd Mercher from dies Mercurii "day of Mercury"
- dydd Iau from dies Iovis "day of Jupiter"
- dydd Gwener from dies Veneris "day of Venus"
- dydd Sadwrn from dies Saturni "day of Saturn"
- dydd Sul from dies Solis "day of the Sun"