a·corn (ākôrn′, ākərn)
The fruit of an oak, consisting of a single-seeded, thick-walled nut set in a woody, cuplike base.
[Middle English akorn, from Old English æcern.]
Word History: A thoughtful glance at the word acorn might produce the surmise that it is made up of oak (from Old English āc) and corn, especially if we think of corn in its sense of "a kernel or seed of a plant," as in peppercorn. The fact that others thought the word was so constituted partly accounts for the present form acorn. Here we see the workings of the process of linguistic change known as folk etymology, an alteration in form of a word or phrase so that it resembles a more familiar term mistakenly regarded as analogous. Acorn actually goes back to Old English æcern, "acorn," which in turn goes back to the Indo-European root *ōg-, meaning "fruit, berry."
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Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.