The hawk cocked her head and glared at me, her eyes gleaming golden with determination. She wanted to know if I was serious about the job at hand.

“Just do like I showed you before,” said Joe Healy-Rennison, my instructor and fellow pack member at Ireland’s School of Falconry. He encouraged me in his easy Irish manner, pushing a freshly severed chicken foot into my gloved fist. Then I stuck my left arm straight out to the side, tensing my shoulder as Lima, the beautiful brown Harris’s hawk, swooped down in a gush of wind, lighting upon the edge of my covered wrist. I rotated my hand as her sabre-like beak snapped up the chicken foot. She swallowed it whole, shaking her gullet, then blinked with satisfaction.

We were hunting for small game in the vast forest – some 350 acres of thick woodlands – surrounding historic Ashford Castle at the northern tip of Lough Corrib in western Ireland. As we stepped deeper into the ancient woods, massive tree trunks rose up like Greek columns with a vaulted ceiling of green, heart-shaped leaves. The day was warm and overcast, a dry spell following the wet and gloomy Irish morning.

“Hold onto Lima,” Healy-Rennison commanded, as I tightly pinched the speckle-feathered bird’s jesses, or tethers, under my thumb.

“Now she’s ‘under your thumb’,” Healy-Rennison explained with a smile.

“Quite literally,” I replied, amused to learn the etymology of a phrase that I’ve used for most of my life. Only now I was standing in the place where the phrase was born – in the wet green woods of the Anglo-Irish gentry, with a giant hawk on my wrist, her jesses wrapped around my little finger. “Yet another phrase we get from falconry,” said Healy-Rennison, who advised me to add the extra grip of my pinkie.

Healy-Rennison then covered the bird’s eyes and head with a small leather hood to keep her from distraction until we reached our hunting spot.

“Hence the term ‘hoodwinked’,” he said cheerily, continuing to teach me English – the English of 16th-century falconry, a rare jargon that entered the colloquial, thanks in part to one amateur falconer, William Shakespeare. Experts still argue about how much falconry Shakespeare actually practiced in real life, but he was no doubt personally acquainted with the sport, as his plays carry more than 50 references to falconry.

Macbeth advises “scarfing the eye”, a reference to hoodwinking a falcon to prevent the bird (his lady) from distraction. He continues the falconry metaphor with holding the lady back on her perch while other falcons prepare to “rouse”, or take flight. French terms like “rouse” (from the Old French ruser, when a hawk shakes its feathers) entered English with the Norman invasion of 1066. But it is Shakespeare who helped forge a new meaning: “to rouse” as in “awaken”.

Lima only roused slightly when I removed her hood, fluffing out her feathers before settling back into to her sleek, sharp self. Then she hurled forward, dashing upwards into the highest tree.

My eyes searched the dappled camouflage in front of me – tree limbs, leaves and shadow – but I could not see her.

“Just keep walking,” Healy-Rennison instructed. “She sees us far better than we can see her.”

“Eyes like a hawk,” I mused aloud, treading onward.

“Ten times stronger than a human’s eyesight,” said Healy-Rennison, adding, “Like reading a newspaper across a football field.”

I adjusted my glasses, squinting at the luxuriant blur and feeling even more inferior to the half-kilo bird that was teasing me deeper into the forest.

From medieval falconry to modern English

Bate Birds beating their wings while still tethered; from the Old French batre (to beat), eventually “to hold back, restrain”, as in a bated breath.
Booze From the 14th-century verb bouse (Dutch origin), to drink excessively. A bird that drinks too much water will not hunt, similar to those who are “fed up”.
Fed up A bird that is no longer hungry has no incentive to hunt.
Haggard A wild hawk that’s difficult to train. One of Shakespeare’s favourite terms.
Hoodwinked To prevent a bird from immediately searching for prey, falconers cover the bird’s head until they are in the right place to hunt.
Rouse From the Old French ruser, when a hawk shakes its feathers. Figurative meaning “awaken” first appeared in late 16th-century England.
Under his thumb Tightly gripping the jesses, or tethers, under one’s thumb prevents the bird from flying away until it is released.
Wrapped around his little finger Wrapping the jesses around the pinkie finger adds an extra anchor in securing the bird.

“There, she’s found something!” Healy-Rennison called, pointing at Lima, who had magically appeared on a high oak limb ahead of us. We both rushed forward like urgent, obedient children. “See how she’s wagging her tail?”

Healy-Rennison pointed upward, and sure enough, Lima was bouncing her tail feathers up and down. “That means she’s spotted something. She’s signalling at us to find it.”

We dropped down to the ground and began crawling around on all fours. My first falconry lesson had reduced me to the same state as the rodents we were hunting, but like the haunting harp music of the Emerald Isle, this is tradition.

Humans have hunted with birds of prey for thousands of years, and for nearly 800 years at Ashford Castle. Built in 1228, the old Norman castle evolved into an elaborate chateau, eventually purchased by the Guinness family and transformed into a Victorian hunting lodge. To that end, the beer barons expanded the estate to more than 26,000 acres (larger than Manhattan), conserving the kind of old-growth forest that once covered the whole of the British Isles.

This is what all of Ireland used to look like, I told myself while rummaging in the underbrush under Lima’s watchful gaze. Everything was forest, and filled with fairies, say the legends. Prime leprechaun habitat too, I thought.

“So, they used to hunt mice and squirrels in medieval times?” I asked stupidly.

“Not really – more like rabbits,” Healy-Rennison explained, motioning for me to stand up. “Big rabbits. A hawk like Lima can lift a 5kg hare, easy.” Some still do, given a chance.

I do the maths.

“That’s like me picking up a car!” Healy-Rennison nodded, handing me another chicken foot, and I stuck out my arm. Lima swooped down once more and gobbled up the reward, but we could only repeat this search and retreat game so many times.

“If she has too much to eat, she won’t hunt anymore. Hence the term ‘fed up’.” I looked back at Healy-Rennison, who nodded. Again, the term comes from falconry.

In Shakespeare’s play The Taming of the Shrew, the male lead Petruchio likens taming his new bride to training a hawk:

     My falcon now is sharp and passing empty;
     And till she stoop she must not be full-gorged,
     For then she never looks upon her lure.
     Another way I have to man my haggard,
     To make her come and know her keeper’s call,

A falcon or hawk that is fully gorged, or “fed up” will no longer work for her master. On the other hand, a “haggard” is a wild hawk that may never be fully trained. Shakespeare uses the term five times to describe different women in his plays, which in later English came to mean wild, unkempt and dishevelled.

After two hours crawling through the forest, I was feeling a bit dishevelled myself. My first falconry lesson ended without any kills, but a whole pocket full of new vocabulary.

If you liked this story, sign up for the weekly bbc.com features newsletter, called “If You Only Read 6 Things This Week”. A handpicked selection of stories from BBC Future, Earth, Culture, Capital, Travel and Autos, delivered to your inbox every Friday.