I just played a bit of tiggy with my niece and we made a rule that the bathroom was "barley". That term was around even when I was her age 25 years ago. Basically if a place or object is "barley", it means that you can't catch the person if they are in that place or holding hat object/. Would anyone be able to enlighten me on how it originated? Is it just used in Australia? A friend of mine thought that it might actually be "Bali" with that island's reputation as being a peaceful safe haven, well, except from the period of the two bombings in 2002 and 2004.

It's used in England too - or at least, it was used in London when I was a kid in the '70s. I thought it was 'barley' rather than 'Bali' but couldn't say for sure - and I have no idea about its origins.

I think Iona and Peter Opie who wrote about English children's games in the 1950s or thereabouts, call it "barley". If they speculate about the origin, I forget what they have to say.
We don't use it in the US. What do we use? There's "fins" which you call out (I'm speaking of the 1950s, who knows if it still exists) for a short-term truce or immunity, but that's temporal, not spatial. I vaguely remember zones of safety (not objects you hold for immunity) but can't think of a name.
In tag in the US we call those safe places 'bases.' I think tiggy is the same thing as tag?
"Kings-ex" I'd forgotten that. It's how you called for time out when playing tag. The Dictionary of American Regional English says <blockquote>Quote
<hr>king's ex exclam, n Also king( ' s), king( ' s) sax, king ' s (s)cruse; for addit varr see quots [Cf EDD king ' s, ~ cruise, ~ ground, ~ speech (at king sb. 10, 1.[13], [23], [45]). According to 1959 (1967) Opie- Opie Lore Schoolchildren 141- 53, kings and crosses are common truce terms in ceEngl; (s)cruce(s) and exes are also attested. Although ex is often assumed to be an abbr for excuse, it seems more likely that it, as well as (s)cruce(s) and crosses, refers to the act of crossing the fingers, often an essential part of claiming a truce or time out.] chiefly west of Missip R, Gulf States, Ohio Valley ... Cf fins 2, time out Used to demand a pause, exemption, or truce during a fight or game; the momentary truce or state of immunity so demanded.<hr></blockquote>I never heard of "fins" until I was an adult. We called the safe place or thing "base."
From a BritishLibrary site <blockquote>Quote
<hr>Traditional children’s games and songs are a rich source of regional words. Even the simplest game of chase has a number of different names that vary according to where you are in the UK – it, tig, tag or tiggy. Research by Peter and Iona Opie in the 1950s and 1960s also unearthed an enormous range of regional truce terms, such as barley, scribs, fainites, pax, skinchies, cross keys and full stop. These are all words or phrases children shout while crossing their fingers to indicate they are briefly withdrawing from a game of chase and therefore cannot be caught. <hr></blockquote>
From some usenet and forum discussions (>denotes a new post. If there is no space, the posts are related):
>The Opies found a huge variety of "truce terms" in use in the 1950s, including a whole group - vains, fains, fainites, fanlights, fainsies, fennits, fans, fainies, vainlights and vainyards - based on the medieval English phrase "fain I" meaning "I decline", from old French "se feindre" meaning "to make excuses, hang back, back away from a fight". This derivation was first put forward by J R R Tolkien (whose day job was course was Professor of English Language and Literature at Oxford) who noted in this context a line in Chaucer "lordes heestes mowe nat be y-feyned" meaning "lords' orders cannot be answered with a 'fain I' [but must be obeyed]". (I'll bet "fins" is in this category--N.)
>[from the OED]'Fains', or 'Fain it'{em}A term demanding a 'truce' during the progress of any game, which is always granted by the opposing party. Ibid. 517/1 A boy who had 'killed' another at marbles, that is hit his marble, would call out 'Fain it', meaning 'You mustn't shoot at me in return'; or if a boy was going to shoot, and some inequality of surface was in his way, which he would have cleared away, his antagonist would prevent him by calling out 'Fain clears'.
>Keys is supposedly a corruption of Kings. I believe it is viking because it is only found in the danegeld areas. When children are playing tig and want a rest they cross their fingers and shout 'Keys', that means they can't be tigged until they rejoin the game. Interesting that you, too, call the game 'tig' though. This isn't universal either. When we called 'barleys' we'd hold both hands out with elbows bent and with thumbs up and fingers curled - slightly different from crossed fingers, but it seems to have meant the same thing.
>In Cumbria (Keswick at any rate) we called it 'tiggy'. And what you called 'keys'/barley, we called 'skinch'.
>[Australia] Tiggy is actually short for 'Tiggy Tiggy Touchwood'. One person is nominated to be 'it' and must try to tag the other players. They are safe so long as they are touching something made of wood but can only do so for a certain period.
>We used to play a game we called 'tiggy' and it was like what you described with the exception of the wood... sometimes it included 'barley' which means a player could be 'barley' if they were at a certain spot, or they were injured or something.
>We also used to generally nominate an area of playground to be 'den' where you could go and stand without getting tigged.
This has a discussion of New Zealand truce terms. Nova Zelandia est Omnis Divisa in Partes Tres<blockquote>Quote
<hr>The commonest truce term in NZ is pegs (or one of the variants pegsed, pags(ed), pex or the likely original term, pax). Poison and bags are also fairly widespread<hr></blockquote>

In the southwest US we used "base" for a safe place to stand (such as a circle drawn on the ground) or touch (such as a tree). A temporary pause was "time out" ("times" for short), "king's ex" or "safeties".