The phrase to turn up one’s toes, or to turn one’s toes up, means to die.

The earliest instance that I have found is from an article about the massacre by coolies of the crew of the American ship Robert Bowne, as reported by Hong Kong newspapers, published in The Sun (Baltimore, Maryland) on 12^th August 1852:

One of the coolies came across the medicine chest, or rather the place where the medicines were kept, and thinking he had fallen in with something very nice, took one of the bottles containing some liquid, set himself down, and emptied it, eating biscuit with it. About three hours afterwards he turned his toes up!

The earliest occurrence of the adjective toes up, which means lying dead, that I have found is from The New Sporting Magazine (London) of December 1841, which published under the title A breeze amongst the Lions a letter that one Captain G. Grenville Malet had written on 18^th August 1841; this is what happened after one lion was killed:

The other gave us some work, for the stuff was terribly thick; at last he also rushed upon us without any warning, and kicked up a proper delight immediately under us. He was very savage, and in fact made himself as disagreeable as possible. He could have liked to have eaten us, elephant and all. We at length, by severe peppering, made him cut his lucky, and found him toes up within a few yards.

The phrase to turn up one’s toes might have originated in the Irish-English phrase to turn up one’s toes to the roots of the daisies; the earliest instances that I have found are in the passive form with one’s toes turned up to the roots of the daisies, and variants, meaning lying dead.

(Two other colloquial phrases associate daisies with being dead: under the daisies, which means dead and buried, to push up (the) daisies, which means to be in one’s grave, to be dead.)

The earliest occurrence that I have found is from The Courier (London) of 28^th August 1830, which published “From a Tombstone in Ballyporeen Churchyard” (Ballyporeen is a village in County Tipperary, Ireland):

Here at length I repose—
And my spirit at aise is—
With the tips of my toes,
And the point of my nose,
Turn’d up to the roots of the daisies.

In the following months and years, several newspapers republished this epitaph in various forms; for example, this is “An Epitaph, from an Irish Church Yard”, published in the Public Ledger, and Daily Advertiser (London) of 7^th November 1831:

Here at length I repose,
And my spirit at ase [sic] is;
The pint [sic] of my nose
And the tips of my toes,
Turned up to the roots of the daisies.

The Irish-English origin of with one’s toes turned up to the roots of the daisies is mentioned in this extract from an address that a Chartist delivered in Bolton, Lancashire, and that The Manchester Guardian (Manchester, Lancashire) published on 4^th May 1839 in reported speech (Chartism was a parliamentary reform movement):

The present petition was merely a notice to quit, to the house of commons […]. They (of the convention) had not yet decided whether the members must go out at the door or the windows! Or whether they must go out on the Abbey side, where their ancestors lay, as the Irish say, with their toes turned up to the roots of the daisies; or whether they (the convention) would turn them out on the Thames side!!! It did not matter which; but [illegible] they must go, either by hook or by crook!!!