First of all, what is a duplifix? A duplifix is a kind of an affix. An affix is a morpheme (the smallest part of word that carries a meaning) that is attached to a root (a free morpheme that can usually exist on its own) or a stem (a set of morphemes that already creates a word). Consider this example:
The word “misunderstanding” contains one root (“stand”), two prefixes (“mis-“ and “under-“), and one suffix (“-ing”). Prefixes are put before stems and suffixes are put after them.
However, these are not the only affixes English has. Consider another example:
The word “thermometer” contains two roots (“therm-“ and “meter”) and one interfix (“-o-“). It is called interfix because it is inserted between roots.
OK, but you are still asking: what on Earth are duplifixes and where can we find them?
Duplifixes are morphemes that are created by repeating. Traditionally, they are found in languages like Dakota, Somali, Indonesian, Samoan, Greek or Latin. For example, while “alofa” means “he / she loves” in Samoan, “alolofa” means “they love”.
In English, such examples are more likely to occur in the colloquial language rather than the official one.
One example of a duplifix in English occurred in the Wendy Williams Show. Wendy Williams, a TV presenter, was discussing a feud between Katherine Jackson (the mother of famous musicians Michael and Janet Jackson) and her nephew, Trent Lamar Jackson. Katherine Jackson was reportedly scared to return home after she had visited her daughter Janet and grandson Eissa because of the abuse by Trent Lamar Jackson.
“Look, all I know about Trent is that Trent’s father is Joe Jackson’s brother. So he is a real Jackson. A Jackson Jackson,” Williams said. (Joseph Jackson is Katherine Jackson’s husband and father to Michael and Janet Jackson.)
Williams said "Jackson Jackson" to indicate that Trent Lamar Jackson was directly related to the famous Jackson dynasty rather than a random person sharing the same surname. (Remember, Jackson is the 13th most frequent surname in the US.)
Other examples may be found in academic papers, too. Gila Ghomeshi, Ray Jackendoff, Nicole Rosen, and Kevin Russell studied this phenomenon and presented it in their collaborative paper:
“I’ll make the tuna salad and you make the salad-salad.”
“Is he French or French-French?”
As you can see, this process aims to create contrast between people, concepts or things that fall under one word. This is the reason why it is, in case of English, called “contrastive reduplication” - you create a contrast by repeating the segment once more.
So, next time an English-speaking person offers you a “steak-steak”, don’t assume they must be stuttering - they may just be giving you succulent meat with no tofu inside!