Thank you for the information.

Reading up on it, it looks like the practice ended around the beginning of the 20th century

However, there is no written evidence of the practice being used after 1900.[43]

The Wikipedia article on Welsh doesn't go into any detail about its suppression beyond that time. It took Wales about 100 years (Act in 2010) to establish Welsh as a nationally recognized language. That's why I was asking the questions. What happened in those 100 years for Welsh not to develop?

Regardless, the language is listed as "vulnerable" but numbers are picking up again. Since there aren't that many Welsh people in existence, I imagine the max number of speakers is quite limited. For the number of C programmers to drop below it, it'll probably be another 50-100 years. If ever.