The Cornish word, pymp, regularly has schoolboys in titters as well, I'm sure -- pronounced pretty much the same way as Welsh pump but the spelling brings it even closer to English pimp.
(And "sister", chwaer in Welsh, is whor in some spellings of Cornish. More titters. Also with poos "heavy", related to Welsh pwys "weight".)
Can you explain why in a previous example pump was written as bum in "ydy hi'n bum munud wedi saith" and here it's "ydy hi'n bump o r gloch". Ibis said in the comments on the previous example that a soft mutation follows yn when it is introducing a noun e.g 5. So why is the 5 in the previous example different (bum) to the 5 in this example (bump) ,- I'm really confused
The course notes explain this sort of thing. See the sticky discussion 'course hints and tips' here - https://www.duolingo.com/topic/924/hot
In short, the numbers pump, chwech and cant all drop their final letter when used directly before a noun or adjective:
- pum cath - five cats
- chwe beic - six bikes
- can afal - a hundred apples