name check - people used to say, 'I'll give you the name' or 'can you tell me your name?' Now they say, 'I'll do a name-check'. I suspect people think it sounds busy-busy and modern. Or something.
put your foot in it - the it you put your foot in is your mouth. This leads to the kids' gag: 'Every time he opens his mouth, he puts his foot in it.'
put your oar in - the place where you put your oar is probably the water but metaphorically it's a conversation. It can work both ways: 'No one needs you to put your oar in.' Or 'Excuse me, but could I put my oar in on this one.' Quite why the minority sport of rowing has given this idiom is mystifying. Unless it's a sideways nod to boating lakes.
triumphalism - miserablism - the political background to this is based in left politics where both of these terms are used as swear-words. Triumphalism is talking as if we've won more than we've won, and miserablism is making a virtue out of saying how miserable, poor and wretched we are and this will enable us to win.
cleverdickery - talking as if you're cleverer than you are - but we're all supposed to do that now, according to cv coaching and the like.
networking - meet and greet- mingle - circulate - I think 'networking' came in about 1995. Before that, people used to do the other three terms here: circulate, mingle and meet and greet. I wonder if networking works. Surely by now, when someone makes a bee-line for you, don't you think, Uh-oh,here comes some bloody networker, you're not going to get my phone number, pal?
blow the gaff - spill the beans - let the cat out of the bag - whistleblower - leak People get put in prison for doing this, and it's clear that all governments everywhere hate it. In the UK, the Freedom of Information Act came in, and in theory this should have meant that no one didn't ever need to blow the gaff ever again. In fact, cunning governments now set up institutions - like Academy Schools - which are inexplicably exempt from the FOI. Presumably at some point soon, someone from inside an Academy will blow the gaff.
hostage to fortune This is one of those phrases that people use on TV and Radio political discussions. Interviewer: But doesn't that leave a hostage to fortune? Interviewee: Er..yes. I think it means that you say something which might then end up with you being 'hung out to dry'. So it's saying something eg 'When I am Prime Minister, I will give everyone £400 pocket money a week' and then when you become Prime Minister people remind you of it.
keep your powder dry It was always a good idea to keep your gunpowder dry but my mother used to keep the powder she put on her face pretty dry too. If you keep your gunpowder dry, you'll be in a better position to kill someone when it's time to use the gunpowder. It'll work. So, if you keep your gunpowder dry when you're talking, you don't say everything, you don't commit yourself, you reserve judgement. The only problem is here is that that would be more like not firing your gun or cannon, rather than just being a good housekeeper.
whitewash Most government reports are whitewashes, because they cover over the sins of omission and commission just as a painter washes a dirty wall.
up himself Not sure if this is truly a rhetorical term rather than a general character assassination. However, if someone says something a bit vain, like: 'I think I'm really better qualified than you to talk on the subject', this is referred to afterwards in the pub as 'him being a bit up himself'. As a phrase it certainly conveys an interesting image: presumably it's someone who thinks so highly of himself, he would rather enjoy having it off with himself. Quite a lot of bending needed there, I think.