The letter 'u' in Welsh is pronounced the same as 'i' in English. So the Welsh word for 5 (pump) is pronounced the same as the English word 'pimp'.
I reckon that I was confused by the fact that "pimp" is a Cumbrian dialect word for five.
Although pronounced the same as the Welsh "pump", (because the two languages are so closely related), it is written with an "i" because "u" is still pronounced similar to English "u" (in Cumbrian).
That's really interesting. Is Cumbrian a dialect of English with Celtic influences or a separate Celtic language/dialect?
A separate, yet closely related, extinct language that is currently undergoing a revival.