**at would be "Pompey's Pillar", I think! It was named after their Indian guide's baby. It seems they gave him an affectionate nickname, and it stuck.***
Actually, his name was "Pomp".
Yeah, you're right! When he was born, out on the "trail", he was kicking his little legs, so they said he looked like a "pompous little man", or a little dancing man, or something like that!