A person who brings up a topic or brings something to discussion, or a tool used to enlarge or shape holes.
From broach (to pierce or introduce) plus the agent suffix -er, creating 'one who broaches' either in conversation or with a tool.
A broacher can be both a diplomatic person starting a conversation and a metalworking tool—one broaches subjects, the other broaches metal, showing how the same root action applies across completely different domains.
Complete word intelligence in one call. Free tier — 50 lookups/day.