I recently praised "misunderestimate" as word combining the meanings of "misunderstand" and "underestimate." My fellow-Agoraphilian, Glen Whitman, and I discussed the topic a bit more in the comments to that post. I there wondered what Glen's linguist brother, Neal, would call a word ABC made of word AB combined with word BC. Belatedly, I learned that Neal's had already answered my question on his blog, Literal-Minded. (Glen answered it, too, during our continuing conversation in the comments to my post)
In a passing reference to our debate over misunderestimate, Neal said that I view it "a straightforward portmanteau word, a blend of misunderstand and underestimate, meaning 'to simultaneously misunderstand and underestimate.'" I had to google that linguistic term of art. According to this, this, and this source, a portmanteau word is a word made up of parts of other words. Examples include smog, (smoke + fog), brunch (breakfast + lunch), and motel (motor + hotel). Serious linguists also call such words blends. (Neal's blog entry, you may note, used both terms.)
I must say, though, that I am not entirely satisfied with the application of that general label to misunderestimate. To judge from the illustrative examples, portmanteau or blend words come in many different flavors. They sometime cobble together words that share no overlapping parts. Consider brunch, for instance. Its constitutive words don't have any parts in common. Another such barely-portmanteau word comes to me from Whitman family lore about a running joke between Glen, Neal, and their dad: Frings, which the Fuddruckers restaurant chain uses to denote an order of fries and onion rings. In contrast to those examples, other portmanteau words do have overlapping parts—smog and motel, for instance.
The portmanteau or blend label thus covers too much ground for the job at hand. The class of words made out of other words includes a interesting and distinct subset of words made out of words that share common parts. See, e.g., smog, motel, and misunderestimate. A smaller subset includes only those words made out of words that share common sounds (phones, a linguist might say). See, e.g., motel, and misunderestimate. More specifically—and to my mind interestingly—yet, we might focus solely on words made out of words that share common syllables. See, e.g., misunderestimate.
I've found no taxonomy of portmanteau words that recognizes and names those distinct subsets. That seems a shame. I'll wager that careful study might discover some interesting differences between them, such as the percentage that each category represents of all the words in any given language. Until those categories get names, however, they will probably continue to evade serious scrutiny. Fortunately, it’s a deficiency easy to remedy. I won't tackle the job just now. I've jabbered quite enough about the topic. I do hope, however, that if and when somebody comes up with labels for those various sorts of words, they use appropriately self-referential portmanteau words. Portmanteau itself arose that way, after all, as a blend of the French words porter (to carry) and manteau (cloak).