Really well-written and informative post – thanks!
What’s interesting is “bolloxed” means tired too. 
What is “the Travelling community”?
A polite umbrella term for cohesive groups of people who have no permanent address, move from place to place together, and are of low socioeconomic status. Most are Roma (a.k.a. “Gypsies”), but some aren’t.
(double post)
Not in that context it isn’t. It specifically refers to Irish Travellers, not Roma or other groups.
Very enlightening! My only previous exposure to the term was from Eddie Izzard’s Dress to Kill when he described Swindon as “knackered” and “kind of Fresno”. Having never visited or heard about the reputation of Fresno CA, and being unfamiliar with the expression, I could draw no conclusion as to the civic character of Swindon. Now I have a vague notion of what both Fresno and the home of the (in)famous Magic Roundabout are like.
Fascinating. Estimated 10,000 to 40,000 in USA!
In Ulysses (and no doubt the Wake) Joyce has Stephen Daedalus recite a love poem (meaningless to almost everybody w/o a translation/concordance).
The standard concordance says that it is “gypsy cant.” I dont know the difference between Roma and Traveller cant, but it seems that the encyclopedic Joyce would have anything but an Irish-sourced cant.
I’d be happy to supply line references–or copy over the text of the poem to-- this threadin Ulysses (it is now on-line for free) and the translation of the lines, as given by the concordance (author’s name forgotten at the moment).
Two English words that came from Shelta (Irish Traveller cant): “bloke” and “moniker”.
They don’t bleep it in BBC’s Top Gear and, there, it’s always meant very tired.
Its often used to mean someone having been beaten up, and the shortened version is a verb - to knack someone, is to fight and beat them, or as a threat to knack someone.
If you are in a bad situation you can also be knackered, instead of the rather ruder word - fucked. In the same way as being up shit creek without a paddle.
American here and I’ve never been an editor nor a writer (well, not a professional writer) but I’ve always been a ‘voracious’ reader, and I really can’t recall having ever seen the term in print. YMMV 
It sounds unspeakably quaint to me, like knickers, bloomers, and other terms from my grandparents’ youth.
Knickers is still a common word for ladies’ underwear in England. Not bloomers, because people don’t wear them any more.
Not in the context it was first used in this thread - “chav” is most likely a Roma word, not a Shelta one. It’s possible jjim meant any of the nomadic folk - Roma, Travellers…Crustie Jugglers.
I never considered “knackered” a rude word, I always connected it with horses. Specifically: the knackers is where Boxer gets sent 
It is specifically a term used in Ireland to refer to Irish Travellers. Nothing to do with Roma or anyone else.
What Jjimm said was that knacker is a derogatory term for travellers, that is Irish travellers, but can also be used in a more general sense like the term “chav”. It isn’t, however, typically used to describe non-Irish travellers.
Yup, travelling community in that context = generic nomads of any background. It was just a throwaway “isn’t that interesting?” aside that had just occurred to me.
It is a slang word for “tired” or “exhausted”. It could be considered shocking by the prudish but I hear it frequently and the end of a long day by many of my English friends. I’ve used it myself here in the US and never had anyone react to it.
Sorry I’m a bit unclear. AFAIK the term knacker isn’t typically used (in Ireland) for any travellers other than Irish ones. Do you disagree?