When we were all making fun of this term and amazed they didn't know its slang meaning, we all ignored the obvious literal one, which has nothing to do with sex or Boston:
You steep a teabag in heat, to brew something.
It's been steeped.
Do we, um, get it now? We will. Because we haven't seen the last of these murderers. And it's getting warmer.
And Randall Terry sees his chance, and apparently is quite intoxicated with it.