Tumblebrutus is the alternative name for Bill Bailey. The name is a portmanteau of "Tumbler" and "Brute", making him an energetic, acrobatic character who's also rough and violent - very much a troublesome boy!
Growltiger's Last Stand
His bucko mate, GRUMBUSKIN, long since had disappeared,
For to the Bell at Hampton he had gone to wet his beard;
And his bosun, TUMBLEBRUTUS, he too had stol'n away -
In the yard behind the Lion he was prowling for his prey.