What the heck ARE ingrown hairs?

I have a passing knowledge of anatomy but I have never understood how on God’s Green Earth a hair could possibly lose its way to the surface of the epidermis from a millimeter away! What are they doing? Bumping into the odd bit of sebum or dirt and immediately signalling for a U-turn?

And how come they never seem to happen on my head. Or maybe they do. Yeah, yeah…(Folk-etymology alert!) That’s where the expression hair-brained comes from! The hairs circle back in and
[Ricardo Montalban]
…wind themselves around the cerebral cortex. Mind you these are just babies…Pets…
[/Ricardo Montalban]

What really gives here?

Call me a weirdo but I really like ingrown hairs. I know this eradicates not a shred of ignorance but I feel an overwhelming need to speak out.

Popping a zit is one thing but to extract a long, rather mutant black hair from deep within the epidermis is a challenge. A painful challenge from which one might emerge victorious, hair in hand, or admit failure and develop an infection which might require massive doses of antibiotics.

(did I say that aloud?)

Hair-brained (I think) actually drives from Hare-brained - alluding to the mad behaviour of march hares (boxing with each other in a male-rivalry thing)

Ingrown hairs; I get these from time to time, but it’s usually the result of me having incompletely plucked out a beard hair, I think the blunt, snapped-off end of the hair catches on the skin on it’s way through, but that’s just a WAG.

“What am I doing plucking beard hairs anyway?”, I hear you ask; the answer is here

Now, what about ingrowing hares eh? - can’t answer that, can you?