Why is a cow referred to as a 'head'?

Sometimes you’re just too close to the question to think of it til pressed.

Was talking to a city boy tonight and he asked me why, when I said ‘Grampa sold 150 head of cattle last week’, I referred them as ‘head’. One does not refer to 150 beaks in a murder of crows, or 248 dorsal fins in a school of fish, or 327 probiscii in a swarm of voracious, long-billed, dyspeptic musketoes.

What is so significant about the etymology of a Holstein’s head that it deserves its own name?

Surely you’ve heard the phrase “head count.”

One track mind, and all.

Of course I have. Are the two phrases related? Which came first?

Surely it’s easier to count the legs and divide by four.

It’s a figure of speech known as synecdoche, by which a part is subsituted for the whole (another example would be to refer to a car as “wheels”, or 20 ships as “20 sails”). The OED dates the use of “head” to refer to numbering livestock back to 1513.

Interesting that Chinese uses exactly the same “measure word” for cattle. “three head of cattle” = “san tou niu”. I think this would indicate that there is some practical derivation of such an expression independent of culture–that is, both Chinese and English farmers found it easier to count the heads rather than the feet.

Also interesting is the fact that the English word cattle is derived from the Latin ‘Caput’, meaning head.