On the pictures below is a tool called "bridge cam gauge", mentioned in this answer. I wonder why the words "bridge" and "cam" are used in its name.
I found a definition of "cam" that might be relevant:
A curved wedge, movable about an axis, used for forcing or clamping two pieces together.
As I understand, the 'cam' here is the flat roundish beaky plate that you can rotate about its hinge.
But what about "bridge"? Wiktionary offers a variety of senses, which makes it hard for a non-native speaker of English.
P.S. It is also called "cam type weld gauge"