DOCTOR CAIUS
If dere be one or two, I shall make-a da turd.
from "The Merry Wives of Windsor", Act III, Scene iii
A turd is a piece of fecal matter, human or otherwise. It is derrived from the Middle English word tord, which had the same meaning.
Shakespeare's use of "turd" is a pun on "third", but still makes for some giggles during 8th grade English Literature. The meaning of "turd" in Shakespeare's day was the same as the modern definition, so he knew what he was doing. The Bard was not above using toilet humor to get some laughs from his audience.
In those days, it was common to use "turd" as an insult. Unlike many Victorian words ("naughty", for instance), the derogatoriness of calling someone a turd hasn't changed.
The first time I remember being spanked was for saying "turd". I couldn't have been more than three at the time, and for several years afterward I wondered just exactly what the word meant.
Maybe if I'd been better versed in Shakespeare this could've been avoided.