“A horse! a horse! my kingdom for a horse!”

This well-known quotation is the last line of the penultimate scene in the play Richard III by William Shakespeare.  It is fairly topical as remains found recently in a car park (parking lot) in Leicester have been identified as those of Richard III.

File:Hogarth, William - David Garrick as Richard III - 1745.jpg
David Garrick as Richard III in a painting by Hogarth  Photo credit Wikimedia Commons http://en.wikipedia.org/wiki/File:Hogarth,_William_-_David_Garrick_as_Richard_III_-_1745.jpg

If wishes were horses, beggars would be kings.
This is a proverb or saying.  The meaning is fairly obvious; if we could bring something into existence just by dreaming of it…

A man on a galloping horse wouldn’t notice.
This is reassuring advice when there is a small mistake in a handicraft project, such as an embroidery.  Some errors may need to be corrected, but others are hardly noticeable.

A dark horse is someone with a secret, such as a talent no-one was aware of.  The Oxford Dictionary of Phrase, Saying and Quotation suggests a competitor about whom little is known.

White horses are the crests of waves on a rough sea.

A horse of a different colour is something entirely different.

There is a kind of word game where words are replaced by similar sounding ones.  I have seen this saying rendered as “a hearse of a different killer”.  It was in a book published by MENSA and had a story ending with this line.   The adapted saying is called a feghoot.

Wild horses couldn’t…
are words which introduce the idea that nothing would persuade me to do it.  I haven’t found a derivation, but wild horses might tempt people to go and look at them.

Horseplay is boisterous play, according to the Concise Oxford Dictionary.

Take the bull by the horns means grasp the nettle.

I am not a biologist, but I think it is true that all animals with horns are herbivores – even the extinct ones!

Like a bull in a china shop means without finesse.

It’s the last straw that breaks the camel’s back.
A load can be gradually increased until it is too heavy to bear.  That’s the last straw is often said when a number of things have gone wrong making extra work.

To make a pig’s ear of something is to make a mess of it.  Again handicrafts come to mind.

When our children were young to keep them amused on long car journeys I invented a game, which I called “Hoofs and paws”.  I called out the name of an animal and they had to say whether it had hoofs or paws.

That will separate the sheep from the goats is a saying which comes from the Bible.

In the Gospel of St Matthew Chapter 31 verses 31-46 Jesus tells a parable and explains its meaning.