The following is an annotated version of the fairy tale. I recommend reading the entire story before exploring the annotations, especially if you have not read the tale recently.
JOHNNY GLOKE was a tailor by trade, but like a
man of spirit he grew tired of his tailoring, and wished to follow
some other path that would lead to honour and fame. But he did not
know what to do at first to gain fame and fortune, so for a time
he was fonder of basking idly in the sun than in plying the needle
and scissors. One warm day as he was enjoying his ease, he was
annoyed by the flies alighting on his bare ankles. He brought his
hand down on them with force and killed a goodly number of them.
On counting the victims of his valour, he was overjoyed at his
success; his heart rose to the doing of great deeds, and he gave
vent to his feelings in the saying:
'Well done! Johnny Gloke,
Kilt fifty flies at one stroke.'
His resolution was now taken to cut out his path to fortune and
honour. So he took down from its resting-place a rusty old sword
that had belonged to some of his forebears, and set out in search
of adventures. After travelling a long way, he came to a country
that was much troubled by two giants, whom no one was bold enough
to meet, and strong enough to overcome. He was soon told of the
giants, and learned that the king of the country had offered a
great reward and the hand of his daughter in marriage to the man
who should rid his land of this scourge. John's heart rose to the
deed, and he offered himself for the service. The great haunt of
the giants was a wood, and John set out with his old sword to
perform his task. When he reached the wood, he laid himself down
to think what course he would follow, for he knew how weak he was
compared to those he had undertaken to kill. He had not waited
long, when he saw them coming with a waggon to fetch wood for
fuel. My! they were big ones, with huge heads and long tusks for
teeth. Johnny hid himself in the hollow of a tree, thinking only
of his own safety. Feeling himself safe, he peeped out of his
hiding-place, and watched the two at work. Thus watching he formed
his plan for action. He picked up a pebble, threw it with force at
one of them, and struck him a sharp blow on the head. The giant in
his pain turned at once on his companion, and blamed him in strong
words for hitting him. The other denied in anger that he had
thrown the pebble. John now saw himself on the high way to gain
his reward and the hand of the king's daughter. He kept still, and
carefully watched for an opportunity of striking another blow. He
soon found it, and right against the giant's head went another
pebble. The injured giant fell on his companion in fury, and the
two belaboured each other till they were utterly tired out. They
sat down on a log to breathe, rest, and recover themselves.
While sitting, one of them said, 'Well, all the king's army was
not able to take us, but I fear an old woman with a rope's end
would be too much for us now.'
'If that be so,' said Johnny Gloke, as he sprang, bold as a lion,
from his hiding-place, 'What do you say to Johnny Gloke with his
old roosty sword?' So saying he fell upon them, cut off their
heads, and returned in triumph. He received the king's daughter in
marriage and for a time lived in peace and happiness. He never
told the mode he followed in his dealing with the giants.
Some time after a rebellion broke out among the subjects of his father-in-law. John, on the strength of his former valiant deed, was chosen to quell the rebellion. His heart sank within him, but he could not refuse and so lose his great name. He was mounted on the fiercest horse that ever saw sun or wind, and set out on his desperate task. He was not accustomed to ride on horseback, and he soon lost all control of his steed. It galloped off at full speed, in the direction of the rebel army. In its wild career it passed under the gallows that stood by the wayside. The gallows was somewhat old and frail, and down it fell on the horse's neck. Still the horse made no stop, but always forward at furious speed towards the rebels. On seeing this strange sight approaching towards them at such a speed they were seized with terror, and cried out to one another, 'There comes Johnny Gloke that killed the two giants with the gallows on his horse's neck to hang us all.' They broke their ranks, fled in dismay, and never stopped till they reached their homes. Thus was Johnny Gloke a second time victorious. So in due time he came to the throne and lived a long, happy, and good life as king.
Jacobs, Joseph, ed. More English Fairy Tales. New York: G. P Putnam's Sons, n. d.