I have a couple of networking components in my rack that take giant AC adapters ("power bricks") that don't fit neatly into my rackmount PDU.
I have one "thingy" that is shown below, and I need to buy a few more. But I have no idea what I'm searching for because I don't know what the "thingy" is called.
Yes, this drawing is terrible. I would ask my 4-year-old to draw it for me because she's a better artist, but she's taking a nap.
I would just call it a "very short extension cord", and in fact a Google search for "short extension cord" turns up lots of results of exactly what you're looking for. E.g., these, which have a pass-through plug.
"pigtail" is a common term for these (actually any 6" to 1' power cord) in the datacenter environments I've worked in.
You can also get short Y power cords.
These cables (including the single variety) are sometimes called "outlet savers".
I also love the 90° rotating plug variety for some applications. The cord goes flat against a wall.
I think the official name is "Power Strip Liberator".
Google image check: http://www.google.com/images?q=power+strip+liberator
UPDATE:
Sorry, I think that's a product's name (trademark), not the common name for the "thingy." But I looks like that the product is the "Coke" amongst power extension cords. :)
It is called a pigtail extension cord. http://www.mockett.com/pt1-90.html
It's just a short extension cord, like this one from Startech.com.
it is called: 1ft Power Extension Cord.
I found same here: http://www.cablewholesale.com/specs/power-cable/10w1-04201.htm
'Very short A/C Extension' ? That's what I Googled and came up with this
EDIT: 6 inch version at Radioshack
Its called a "Wall wart remover".
Um, an extension cord? (Needed 8 more characters for valid answer)