Echnos is such a useful word!
Watch out for mispronunciation of Lingo
Echnos: would "The night before last" have the same meaning?
Yes, that's exactly what it means.
why do i need the article "the" before the word night? I don't see anything in the Welsh sentence to indicate that the article exists. Is it something specific that requires the article?
Welsh does not use the definite article in this pattern, whereas English does.
A word for word translation often does not work well between the two languages,
Why isn't it 'Gwelodd hi Ddewi Lingo echnos'? I thought objects of conjugated verbs receive a soft mutation.
Personal names generally resist mutation.