Since the 1500s, the word "periwinkle" has been used as the name of two distinctive items: an edible sea snail and a broadleaf evergreen plant—or, in its adjective form, the color of said evergreen plant. Both have different but converging etymologies.
"Squid" is thought to be a sailors' variant of "squirt," referring to the ink ejected by the cephalopods. Commonly used as the name of the fried culinary dish, "calamari" is also the name of a specific genus of squid and comes from the Latin calamarius, literally "pertaining to a pen."
An unpaired word is a word that doesn't exist in common use without a prefix or a suffix, or has no natural opposite, like "debunk," "reckless" and "unscathed."
I wrote a book about etymology! It's called ONCE UPON A WORD: A WORD-ORIGIN DICTIONARY FOR KIDS.
Useless Etymology 