Milk 

At the risk of clubbing you over the head with facts you already know, human beings are mammals, which means we drink milk - our milk - not milk that comes in cartons of the cold section in the supermarket.
Here's a puzzle: why, then, in English and many other languages, does the word 'milk' first connote the milk of cows? or of sheep or goats? Why doesn't 'milk' immediately conjure warm, sweet and creamy sustenance fresh from the breast? Why, when we think of dairy-maids, are we not imaging rosy-cheeked lasses tweaking the last of the cream from their plump bosoms?
We accept that it is normal to drink milk intended for the young of other mammals. It isn't hard to see the benefit of consuming such a rich and readily available food. Isn't it strange though that we have forgotten that first and foremost 'milk' comes from us?

When my son was born he was placed on my chest to find his way to the locus of his nourishment for the next twelve months. I was reminded of a picture of a newborn kangaroo I had seen in a nature book when I was a child. It looked like a little pink jelly baby that someone had sucked and spat out, stuck to a fur coat. Blind and with a gaping, searching mouth it was less than a centimeter away from the nipple. That picture had made me feel so frustrated, like I wanted to give the baby joey a prod towards its goal with my finger and shout "To the left, dammit! Just a little to the left!"
Rufus was exactly the same. He clawed at my breast and, desperate for something to suck, thrashed his head blindly from side to side like Stevie Wonder.
To anybody who hasn't attended a prenatal breastfeeding class, you would think getting a baby to drink milk from its mother's breast was straightforward: place object A (baby's mouth) on object B (nipple) and voila! - all night milk bar. Instead I had been shown a far superior technique that involved trying to hold the baby like a football and position his head with my elbow while trying to manipulate my nipple into the proper configuration to get as much of it into his poor little gob as possible.
It was far more frustrating than the baby kangaroo photo.
Thankfully my sister-in-law came to visit the next day and said " I don't want to give unsolicited advice, but have you tried holding him comfortably and putting his mouth in front of your nipple?" Bless her and bless the bleeding obvious.
My little mammal knew what to do.

The Wellcome Museum in London has a wonderful collection of milk related objects including a teat cut from the udder of a cow to be used with a bottle for feeding. In its day the surrogate teat wouldn't have raised an eyebrow, let alone a shudder.

We buy the milk of other mammals in bottles at the supermarket. Our strange customs lose their strangeness with the familiarity of the everyday.