Green’s Dictionary of Slang

settler n.

1. a parting drink, ‘one for the road’ [such a final drink supposedly ‘settles’ the stomach after an evening’s indulgence].

[UK]M. Bishop Life and Adventures 124: I endeavoured to revive them by saying I intended to have a Bowl of Punch, by way of a Settler and then to go to Bed upon it [OED].
[US]Wkly Rake (NY) 9 July n.p.: Well, Tom, we have not time to go at you this week; but give us one more good settler, and next Saturday we’ll gratify you.
[Aus]M. Clarke Term of His Natural Life (1897) 66: Having got out the rum bottle for a quiet ‘settler’.

2. a knockout blow, esp. in fig. use, i.e. something that brings things to a conclusion.

[UK]Morn. Chron. (London) 16 Aug. 3/5: Martin availed himself of his superior legnth [...] and finished the round with a ‘settler’ on the ‘lug’.
[UK]‘One of the Fancy’ Tom Crib’s Memorial to Congress 15: So he tipp’d him a settler they call ‘a Spoil-Dandy’ / Full plump in the whisker.
[UK]Vulgarities of Speech Corrected.
[UK]Cruikshank & Wight Sun. in London 77: Mizzle home. Wife sings out. Give her a settler. And so turn in; – rather muzzy.
[UK]Exeter & Plymouth Gaz. 3 Oct. 4/2: This was what he termed a ‘settler,’ and he gave in.
[US]Flash (NY) 2 Oct. n.p.: Em gave her a settler in the knowledge box.
[US]‘Ned Buntline’ G’hals of N.Y. 68: That dig in the side was pretty good; but the settler wos in the back bone – that wos wot fetched him!
[UK](con. 1846) Fights for the Championship 214: It was evident the last hit had been a settler.
[UK]J. Greenwood Little Ragamuffin 21: I was overtaken and passed by a tall gentleman in black clothes [...] This, of course, was a settler for me.
[UK]Sportsman 22 Dec. 5/6: A mistake at the last hurdles proved a complete ‘settler,’ and he succumbed by six lengths .
[US]Nat. Police Gaz. (NY) 21 Dec. 10/4: [pic caption] Lynch’s Settler.
[US]A.C. Gunter Miss Nobody of Nowhere 154: That will be an absolute settler to the slightest suspicion of a doubt.
Dly Signal (Crowley, LA) 8 Sept. 2/1: A sockdolager is a slang word [...] often used for a knock-down blow, a settler or coup-de-grace.

3. (US gambling) a variety of crooked dice used in craps.

[Aus]Truth (Brisbane) 13 Nov. 9/3: Other [dice] are loaded, and these are known as ‘old settlers’; they settle on the loaded side.

Aus. uses in context of SE settler

In compounds

settler’s clock (n.) [i.e. it wakes one up]

(Aus.) a kookaburra.

[Aus]F.G. Aflalo Natural Hist. of Aus. 114: From its habit of starting its discordant paean somewhere near sunrise and, after keeping comparatively quiet all through the hotter hours, cackling a requiem to the day’s decline, the bird has been called the Settler’s clock.
[Aus]Stephens & O’Brien Materials for a Dict. of Aus. Sl. [unpub. ms.].
[Aus]Brisbane Courier 22 Nov. 19/6: The laughing jackass [...] used to be the bushman’s (or settler’s) clock.
[Aus]Western Mail (Perth) 11 Sept. 30/3: He is also known as [...] Greart Laughing Jackass, Bushman’s Clock or Settler’s Clock.
[Aus]N. Pulliam I Travelled a Lonely Land (1957) 235/1: laughing jackass – one nickname for the kookaburra [...] Other names are: jacky, jacko, alarm bird, bushman’s clock, clock bird, settler’s clock or shepherd’s dock, woop-woop pigeon, etc.
[Aus]G. Seal Lingo 59: jacko (also used in Australia for Aborigines, though once applied to the kookaburra, from one of its Lingo names the laughing jackass. The call of this bird was also known as the settlers’ clock during the 19th century.).
settler’s matches (n.)

(Aus.) easily lit strips of bark, used to light fires.

Australiasian 13 June 1133/1: Re settlers’s matches, torches, the blacks in the South-east of South Australia always used the bark of the sheoak to carry from one camp to another; it would last and keep alight for a long time and show a good light to travel by.
H. Lawson When the World Was Wide 84: In the silence of the darkness and the playing of the breeze, / That we heard the settlers’ matches rustle softly in the trees.
[Aus]Stephens & O’Brien Materials for a Dict. of Aus. Sl. [unpub. ms.].
[Aus]Baker Popular Dict. Aus. Sl.