Centrifugical pumps are rated in head. Depending on the liquid being pumped, the pressure will vary with density, however, the pumping action similarly varies with density, so a given pump will produce the same head when pumping oil, water, glycol, etc.
I suppose “head of cattle” is used because it implies that they’re still on the hoof. Once they’re slaughtered you just have beef, and I expect that the head is basically thrown away and you don’t have it anymore.
Now for the big question…
Why is a lettuce called a head of lettuce? I can vaguely imagine some kind of animal with a head made out of lettuce, but that image is seriously starting to freak me out.
City Slicker: Look at that bunch of Cows.
Cowboy: Not bunch; herd.
CS: Heard of what?
Cb: Herd of cows
CS: Why would I care what a cow heard? I’ve no secrets from a cow!
Or an ear of corn? Maybe just because of similar shapes.
I am not trying to hijack this thread, but I have a similar inquiry; and the posts provided so far on this thread lead me to believe one of my fellow dopers will have some insight.
How did the term dead head come into use for both transportation and pumping of liquid materials?
This is by no means meant to disparage those “Dead Heads” who used to follow one of my favorite bands, the Grateful Dead, but I believe the term was in use for a fairly signigicant period of time before Jerry Garcia and the Dead started touring!
of course - I meant “significant”
Originally, in the early 19th Century, someone admitted to a theatrical performance without charge.