From The Collaborative International Dictionary of English v.0.48:
Growl \Growl\ (groul), v. i. [imp. & p. p. Growled (grould);
p. pr. & vb. n. Growling.] [D. grollen to grunt, murmur, be
angry; akin to G. grollen to be angry.]
To utter a deep guttural sound, as an angry dog; to give
forth an angry, grumbling sound. --Gay.