Idioms, what do they mean?

[Undertoad]

It set off my BS meter.

http://www.snopes.com/language/phrases/wagon.asp

[Shawnee123]

Originally Posted by Undertoad

It set off my BS meter.

http://www.snopes.com/language/phrases/wagon.asp

The term "fell for it" (as in "did you fall for that?") can be traced back to 1587, when lepers, returning home from a day of shopping, would trip (or, fall) over their own appendages. Because it was customary in the Middle Ages to point and laugh at lepers, they coined the phrase "boy, that leper really fell for it, didn't he?" It was later shortened to include, not just lepers, but anyone falling over anything.