Sadly, it seems not. My Collins dictionary tells me it's the notochord of a larval tunicate...
...well, at least I know what larval means...
...and, the dictionary continues, slightly more helpfully, typically confined to the tail region.
Right, let's look on the bright side: most of us aren't going to have the slightest need to use the word urochord, are we?
But what is it?
Well, it's the notochord of a larval tunicate.
Hang on, where's that dictionary...
Okay. A larva is an animal at a sort of caterpillar stage of its life, the one when it's hatched out of its egg but turns out not to be in its adult form.
A notochord seems to be a thing a bit like a primitive backbone. Humans have them very briefly while they're developing in the womb, but some creatures hang onto their notochords for life.
A tunicate is a marine invertebrate that's often stuck to the floor of the sea. Here's one sort:
Those are bluebell tunicates. Beautiful, aren't they?
The interesting thing is that, although tunicates look quite different from you, the fact that they have notochords when in their larval state shows that they're actually quite close relatives.
Hmm...perhaps I ought to invite some over for Christmas.
Sunday Rest: urochord. The ur bit comes from the Greek oura, which means tail. The chord bit is also Greek, from khordē, which means gut or string.