Why Do We Say Plumb

Plumb is from the Latin word plumbum, and honestly if you’re not calling every plumber you know a plumbum I think you’re missing a pretty good crack. 

Plumbum means lead. Its first construction usage was in the use of lead weights connected to a string to find a perfectly vertical line, thanks to gravity. We still use this tool, which is a plumb bob. The “bob” part is a weird addition, since it means an up-and-down motion, but I guess it’s possible to make the case for it if you’re spending a lot of time reeling it up and dropping it down again. If you’re catching on to any fishing words in here, it’s because maritime terminology also uses plumb to refer to gauging the depth of water (“plumbing the depths”) using an almost identical process to a carpenter finding plumb. Fishing also uses plumb bob weights, which, of course, are small lead sinkers.

A plumber (plombier in French), then, is someone who works with lead—which, historically, is the material used for pipes. The name stuck, and now anyone who works with pipes is called a plumber (fun side note, in Norwegian a plumber is a rørlegge, literally a pipe-placer). Luckily, our enhanced-belt-cleavage friends don’t have to work with much lead anymore, which is both great for their health and for their bottom line. 

So that’s why we say plumb.