Theory:

Then round and round, and out and in,
All day the puzzled sage did spin;
In vain–it mattered not a pin –
The pigtail hung behind him.

And right and left and round about,
And up and down and in and out
He turned; but still the pigtail stout
Hung steadily behind him.

And though his efforts never slack,
And though he twist and twirl, and tack,
Alas! Still faithful to his back,
The pigtail hangs behind him.
Explanation:
 
The sage was desperate to change the pigtail's position from the back of his head to the front of his face. He jumps across the floor to see if the pigtail would appear on the front. He twists and twirls his body in a random manner to achieve this goal. In spite of being a sage, who is supposed to be wise, he does not have the maturity to understand that the pigtail is a part of his body and that human beings cannot alter the position of something attached to their body. The sage went round and round, seeing the pigtail following his rotating patterns. He then moves in and out, which is one step forward and the other backward. The poet says that it did not even create an effect as small as the size of a pin.
 
man thinking2021-03-03 202522.png
The sage tries to bring the pigtail to his face
 
The pigtail remains in the same position even after the constant jumping. The sage probably wants to bring the pigtail to his face because he wants to see it continuously. He checks on himself to see if everything is perfect. This perfection is what forces him to twist and jump around in different directions. He does not remain calm after one futile attempt. He then jumps right and left, hoping the pigtail would come off as it gets stretched. He then tries jumping in the normal up and down fashion. The poet repeats the words round about, up, down, left, right, out and in, so that it creates the same effect as a person moving. The poem gets the rhythm from these words.
 
The sage's sturdy pigtail hung in his back, no matter what he did. The sage was not a man to easily give up. He continues with his effort despite knowing that his attempts are in vain. He again twists, twirls and tacks, but the pigtail is faithful to the place it had remained and did not move to the face of the sage.
 
man angry2021-03-03 202641.png
The sage tries everything but in vain
 
Words with difficult meaning:
 
S.NoWordsMeaning
1
PuzzleSomething that is not solved
2
SlackLack of energy
3
SteadyFirm and regular
4
TwistTo turn one part of the body while the rest remains the same
5
TwirlTo turn quickly
6
TackTo fasten something
7
DesperateHelpless and worried
8
FutileUseless
9
FaithfulTrue to one's word
10
ConstantForever
Reference:
State Council of Educational Research and Training (2019). Term-3 English Standard-6. A Tragic Love Story (pp 106-108). Published by the Tamil Nadu Textbook and Educational Services Corporation.