You hear the number of cattle that someone has listed as “# head of cattle”.
Why head? If I have 100 head of cattle, I could also have 100 tails of cattle, 200 ears of cattle, or 400 hooves of cattle. Or, I could just have 100 cattle.
Anyone know the reason behind this turn of phrase?
I think it’s because it’s easy to count heads when you’re looking at a group of animals. The heads will have parts that are more easily distinguishable.
The OED says the word in that sense goes back to 1513.
“…it’s easy to count heads …”
It’s also easy to give head for, say, a birthday gift. This was popular among cowboys (and still is).
Well…you may think you have 400 hooves and 100 tails, but what if three cows are missing a leg, two are missing a tail, and one an ear? Well, damn ,that throws off yer numbers, don’t it? But, for a cow to be alive, it has to have a head. So we count the one thing all cows will have if they are live, breathing, able to be milked/slaughtered.
I am, of course, just kidding. But my point remains valid, nonetheless.
a similar question is: why are bullets counted in rounds?
it’s easier to say " 100 cows" than “100 head of cattle” , and
it’s easier to say " 100 bullets" than “100 rounds of ammunition”
I don’t get it.
That’s because the bullet is only part of a round of ammunition, which consists of the bullet, the casing, the primer and the charge.
Yeah but your assuming there is no context such as;
“Bob, how many cattle you got on your ranch now?”
“Oh about 100 head.”
So cows/head and bullets/rounds kind of comes out in the wash.
-rainy
Perhaps because that herd might have 29 steers, 30 bulls, 21 cows and 20 calves? If discussing veal sales, you’d have 25 bovines of interest, but 100 head of cattle for taxation.
Simply saying, “I have 100 head” does not automatically mean cattle. The term “head” is used not only for cattle, but for any livestock mammal like sheep, goats, buffalo, reindeer, swine etc. So if you use head, you must include the preposition to indicate a head of what.
“Head” is synonymous with “general individual.”
We have “head-counts,” “head tax,” and admission prices that are “$x.xx per head.”
Like “head” of cattle, this tells us that we’re talking about something that’s generally inclusive. “Head” is more concise than “men, women, and children*” or “cows, steer, and calves.”
This is the anglicized version of a per capita (“by head”) designation.
I love lightbulb moments.
Ok, as long as we’re talking about head;
What about “a head of steam” ie why is pressure measured in head (feet, meters)?
Static pressure head, dynamic pressure head, etc.? It always makes the boys giggle in my classes. 
To be more clear on my last post, My question is not why pressure is sometimes measured in feet or meters or even inches of mercury (that’s obvious 
), but why is it then called “head”?
“head of cattle” is an example of the grammatical form synecdoche, in which a part is substituted for the whole, the classic example being “red sails at sunset.”
Heh. I just looked up synecdoche in the American Heritage Dictionary, and the example they use is “head [subsituting] for cattle.”
sinjin – my WAG would be that it’s for the same reason we call the foam on beer “head.”
Picture a boiler for a simple steam engine. Water below, steam on top, ready to be piped off. A “head” of steam. Later engineering uses of “head” would be derived from this, wouldn’t it?
Actually, I think the steam usage derived from the earlier use of the term as a measurement of water pressure, as would be used to power a mill.
That does appear to be the case, silenus. link
Teach me to make WAGs in GQ. 
I always thought it was a fun coincidence that Mandarin Chinese - which uses measure-words like “head of cattle” or “sheet of paper” for all nouns - uses the same word - head - to count cattle.
My late great-aunt Ivy, a farm girl all her life, called them beeves, as in, “I have 47 beeves on my farm.”
Thanks Larry and silenus. I’ve wondered about the “head” question for years. I love the Straight dope