porcupine

The word "porcupine" entered English in the late 14th century from Old French porc espin (literally "spiny pig"). This French term was itself a folk-etymological alteration of Old Italian porcospino, from Latin porcus ("pig") + spina ("thorn, spine"). The name reflects a common historical tendency to name unfamiliar animals by analogy to familiar ones, in this case comparing the quilled rodent to a prickly swine. The modern English spelling was solidified by the 16th century, obscuring the original transparent Latin components (porc and spine) within a fused, unsegmentable form.

The word is a loanword from Old French and ultimately Latin, treated as a simplex unit in modern English. It cannot be meaningfully segmented into productive morphemes using its current English spelling.