chomping at the bit / champing
The original verb in the phrase vs. the common replacement.
The original phrase is champing at the bit: a horse working the bit in its teeth. Use champing: They were champing at the bit to start.
Examples
UseThe crew was champing at the bit to start. (eager and impatient)
AvoidThe crew was chomping at the bit to start. (chomping replaces the original champing)
Chomping at the bit is now the more common form, and dictionaries list it. However, many people still consider chomping an error and judge the speaker who uses it.