"Muggle" may mean an ordinary person to JK Rowling, but I remember when it was one of the many synonyms for marihuana.
"HUUMESANASTOA (PDF)
... marihuana hay = marihuana joint = marihuanasavuke kif = marihuana mari = marihuana maris = marihuana mary jane = marihuana muggles = marihuana pat = marihuana ... "
www.finems1.pp.fi/images/huumesanasto.pdf view as html

To give credit where it's due, Anu did mention the use of muggle as a synonym for marijuana(though I'd never heard it before:

"With the fifth Harry Potter book out last weekend, the young wizard
continues his magic on children and adults alike. It's a sign of his
hold on popular culture that muggle, a word coined by the author of
the series, recently made it into the Oxford English Dictionary (OED).
To be precise, the word muggle has been a part of the dictionary for
a long time, even before Harry was born. The OED lists a number of
senses for this word (resembling a fish tail; a young woman; marijuana)
spanning the 13th to 20th century. But Harry Potter books gave a new
meaning to the term...."

Harry Potter books gave a new meaning to the term

With, apparently, the extended meaning of someone who is not proficient in a given field. E.g., computer geeks might refer to us poor mortals as muggles.

Dear AS: Your eyes are sharper than mine. I had to re-read Wordsmith's post again twice before I found it.

computer geeks might refer to us poor mortals as muggles.

Please forgive my muddle, but this leaves me all befuddled: if we mere muggles are poor mortals, aren't the gifted geeks mere portals? :)