Helen said:

You've reminded me of some female surnames: Brewster, Webster, & Baxter (bakster) i.e. , brew-sister, web (or weave) sister and bake-sister, compared with Brewer, Webber or Weaver, and Baker.

Helen, you posted that in 2003. Are you still around?

I never heard that. Can you give some sort of documentation or authentication for that -ster equals -sister bit?

My favorite etymological sourcebook, under teamster, brewster, and several others, merely refers to "a -ster variant of" whatever the verb form is. One exception that might go along with your statement above, and that's "seamstress". Under "sew", going through "Old English seam has derivative seamestre, whence Middle English seamster, whence English seamstress, var. sempstress; seamestre and seamster are feminine; -ess has been added to render the sex unmistakable."

That's the only place I find that kind of connection of a -ster form to feminine, and no direct reference to "sister".

Dave Oesterreich