"Peidiwch dweud!"

Translation: Don't tell!

[Brian_Igiri]

Could this also mean, 'Don't tell'?

[ibisc]

yes

[AngharadJones0]

Paid a ...... was something I heard a lot as a kid

[Banma48]

Does this mean "you don't say!" or just a command?

[areddragon]

It's a command, wch denotes the imperative form in Welsh.

[nebynAmlwch]

Peidio is alway followed by 'â'. It should say 'pediwch â dweud'

[NicDafis]

It's not always followed by â, although it can be. Both forms should be accepted, so report it if it's not.