What is "bog-trotter"

Bog-trotter can mean:

• Slang or derogatory for some types of Irishman: see List of ethnic slurs
• In UK Parliamentary slang, a party's parliamentary whip whose job was, at a parliamentary division, to quickly check round the Parliament building's toilets to check if any of his party's members were in there, as a few members missing at a vote may lose the vote, if the vote is close.