What is the meaning of phellos in the epithet for Quercus phellos, the biological/scientific name for the willow oak? I've tried some obvious resources, but after 50 years in clinical medicine and education, my high school Latin seems to be running out.
That's perfectly understandable, as the word isn't Latin, but Greek. φελλός is the Greek for the 'cork oak', Quercus suber. Why this word was used in the binomial for a different species of oak, I can't say, except to note that since the willow oak is not native to Europe it would not have had a Greek or Latin name.