Compounds are everywhere in English vocabulary, formed by combining two or more independent elements (‘free morphemes’, in linguistic jargon). They can be nouns (living room), verbs (download), adjectives (fun-loving), and other types. They can also be open, closed, or hyphenated, as shown.
The semantic relationship between the parts of a compound varies from one to another. Many are directly compositional; some require additional knowledge. When one element is part of the other, the main one tends to come first and be phonetically stressed: cliff edge, treetop, shoelaces, and so on.
So if we’re talking about the tip or tips of something, that’s the order we expect. Sure enough, there are fingertips, arrow tips, ear tips, horn tips, leaf tips, nerve tips, wingtips, and many more obscure compounds of the same structure. Which leads me to the present puzzle, which I aired first on Twitter:
Why do we stand on our tiptoes and not our toetips? A strange anomaly, is it not? I could neither think of nor find any other tip-X compounds that refer to the tip of something.
Pointe ballet shoes by Petar Milošević
Toetip, the word we would expect, exists. The OED includes it among many toe subentries, defining it as ‘the extremity of a toe’ and offering two 19thC examples, one material (‘Machinery for manufacturing shoe-heels, and toe-tips’), and one anatomical (‘His whole frame laboured to the toe-tips’). Other examples in Google Books give a flavour of its (modest) historical use.
Tiptoes, for all the oddness of its order, has an entry to itself in the OED, and a substantial one at that. The word dates back at least as far as Chaucer:
He moste wynke…And stonden on his tiptoon [v.rr. typton, typtoon, typtoos, tiptos] ther-with-al, And strecche forth his nekke long and smal.
The singular form on (the) tiptoe emerged after a few decades, in the mid-15thC. Much later came the adjective tiptoed (1632) and the verb tiptoe (1661). It is a word beloved by children, who often learn it as tippy-toes, and it is so familiar to us as adults that we overlook its unusual structure.
To my queries came theories. Julian Gough wondered if the verb came first, but the OED’s chronology would seem to preclude this. Others suggested ablaut reduplication – the high vowel–low vowel pattern common to reduplicatives (criss-cross, knick-knack). But while this may help explain why tiptoe spread, I don’t think it explains its origin.
My favourite suggestion came from author Eley Williams (who has a PhD in fictitious entries in dictionaries):
That is, the term began as tipped toes, and the verb’s inflection was assimilated through elision or haplology. Then the phrase was reanalysed as tip toes and fused into one word. That seems plausible to me, but I’m no etymologist, let alone Old English specialist. So I’m open to ideas, or to any work that has explored this curio.
Sentence first 
Reading this whilst standing on my Zehenspitzen, the corners of my mouth started an expedition to the ear-lobes.
I’m happy to hear it. =) Zehenspitzen (“toes-tips”) is sensibly ordered.
I might be misunderstanding this, but what about tiptruck?
A tiptruck (or tipper lorry, etc.), being a truck that tips or tilts, uses a different sense of tip: not the (pointed) end of something.
What about tiptop?
Maybe, yes, if its original derivation was ‘the tip of the top’ and not just a reduplicated form. It’s hard to know for sure. Its first recorded use is in a 1702 translation by Samuel Parker of Cicero’s Tully’s Five Books De finibus:
According to dictionary.com, they define it as the “extreme top or summit” (and a couple of other definitions). I mostly remember it as a child as the brand name of a bread … bloody awful sliced white! As a kid in hospital I had a great nurse whose surname was Whitbread. I nicknamed her “Tiptop”.
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