I mentioned that Stuart Semmel had suggested two NOOBs. The first was “liaise” and the second is second. That’s not double-talk: the word he suggested was “second,” usually used in passive-voice participle form: to be “seconded” (accent appropriately on the second syllable).
The term is of military origin. The OED has a first citation from 1802 and offers this definition: “To remove (an officer) temporarily from his regiment or corps, for employment on the staff, or in some other extra-regimental appointment.” It was applied to movements of civilian employees as early as 1920, when this appeared in the Westminster Gazette: “It was finally agreed that Lord Moulton should be seconded to the service of the Corporation and of the dye industry for..one year.”
This Google Ngram Viewer chart indicates that ever since, “seconded” has been a decided Britishism. (The red line indcates British use, the blue line American)
And truth to tell, it still is one. The first five pages (after which I quit looking) of Google News hits for the phrase are all from U.K. or Commonwealth sources. However, Stuart reports hearing it on occasion in academic circles and my friend Nanette Tobin in corporate ones. And it was used three times in the New York Times in 2016, including this by Sarah Lyall (a longtime resident of London), in her coverage of the New York’s Westminster Dog Show: “Andy Das, an assistant sports editor whose responsibilities typically include soccer and college sports, but who was seconded to dog duty this year…”
So “seconded” is definitely On the Radar.
notoneoffbritishisms.com 
Perhaps muddying the waters a bit: I went to library school in Canada, and within the Canadian library world people are often “seconded” to work at other branches. That was the first time I recall encountering it.
Seconded can also mean supporting someone who wants to join a posh London club.
Also used in connection with a motion at a political rally i.e. ….motion proposed by Brother Smith and seconded by Brother Brown….
I’ve been to enough meetings in the US to know they have that meaning there too. But it is pronounced differently to the secondment meaning. SEK-ondid vs se-CON-ded.
We also talk of going or being on seCONDment.
Pete / Dormouse: SEKond reminds me of the song:
Oh, but if you feel like lovin’ me
If you got the notion
I second that emotion
So, if you feel like givin’ me
A lifetime of devotion
I second that emotion.
One of the great all-time songs, written and sung by Mr. Smokey Robinson.
I do love the challenge of Britishisms, they make me delve deep into the annals of ancestral memory. Here, to second is to confirm a motion, quite a different meaning altogether.
As it is in the UK. But as Ben said, the meaning discussed here is pronounced differently.
It’s used throughout UK business, medicine and education. A teacher can go on secondment to another school, for example, or a doctor to another hospital. Also I think it’s sometimes used when a business sends a member of staff to work pro bono for a charity – i.e. when it’s officially through the business, using business time, such as offering two hours a week of a specific specialist accountant or something like that.
I read it at seconded like when someone proposes something and the other person seconds it. Took me a whole to realise it was like going to work elsewhere. That was confusing 🙂
As a Canadian public servant I have been seconded more than once although we usually use the term to describe the situation when you are employed by one government, e.g. provincial or territorial, and while retaining that employment relationship you are temporarily assigned to work for another government, e.g. federal or another province. If you are working in a different department of the same government you are not seconded but are subject to a temporary assignment. While now we enter into Secondment Agreements that govern the terms of the secondment (length, nature of work, termination) we previously would execute the more august sounding Articles of Secondment, which almost demand a trumpet flourish when you refer to them.