https://www.youtube.com/watch?v=AXqnNokcxlE&feature=youtu.be "Ham" is a common ending in place names, which isn't surprising since it means "village" in Anglo Saxon. Chippenham was the example used in this linguistic trap, but there are plenty of other locations with that suffix. Birmingham for a start. For this word ending, the "h" is omitted entirely and the "a" becomes more like a "u". As a result, the spoken form is more like "um" than "ham". Actually, the way to say Chippenham doesn't stop with the ending. The start of the word has its own peculiar flavour too, just for good measure. Depending on the part of the country in which the word is being said, a tourist might hear "Chipnum" or "Chipenum". Visitors don't stand a chance, do they? Here's a video of the pronunciation used by people in the south of England.