Names have power.
One of the ways the twins gained power of Xibalba is that they learn their names before they meet them.
Then they sent an insect named Mosquito. They sent him on ahead to obtain for
them what he could hear:
Next he bit the third one seated there, who was One Death—“Ouch!” said
each one when he was bitten. “What?” was their reply:
“Ow!” said One Death.
“What, One Death? What is it?”
“I am being bitten!”
“It’s just . . . Ow! What was that? Now I am being bitten!” said the
fourth one seated there.
“What, Seven Death? What is it?”
“I am being bitten!”
[this goes on for some time]
Thus their names were named. Each of them revealed the name of the
other. Each of the individuals in order of their rank had his name
revealed by the one who sat next to him, Not one of their names was
missed until all of the names were named when they were bitten by a
hair that Hunahpu had plucked from the front of his knee. It wasn’t
really a mosquito that had bitten them. And so Hunahpu and Xbalanque
heard the names of all of them.
This allows the twins to name all of the Lords of Xibalba, and thus have power over them.
All of them had their faces revealed, for all of their names were
named. Not one of their names was missed. When they were called upon,
they gave the names of each one without leaving any of them out.
Contrast this to how the parents of the twins were tricked by the Lords of Xibalba because they didn't know their names:
Thus they [One Hunahpu and Seven Hunahpu, the parents of the twins Hunahpú and Ixbalamqué] did not prevail [because they didn't know who the Lords of Xibalba were, and confused them with wooden statues]. Instead, the lords of Xibalba roared
with laughter. They merely roared with laughter, all the lords,
because they had completely prevailed. In their hearts, they had
defeated One Hunahpu and Seven Hunahpu.
(the above quotations are all from the online version of Allen J. Christenson's translation)
This scene recalls other Central American stories where the hero gains power over others through magical projectiles:
But, adds the Quiché account, "in reality it wasn't the mosquito that
bit and went to hear all the names, but rather a hair that Hunahpú
plucked out of his shinbone, and it was this that stung them and
obliged them to say their names."
This clearly defines the magical technique of affecting events from a
distance, through invisible darts that sting like the mosquito but
which really express the personal magical power of the sender. That
method, invented by Hunahpú, a sage par excellence, explains the
origin of an interesting magical practice employed by one class of
Chortí wise men, who "foretell by means of the calf of the leg,"
imitating the pattern laid down by the god-hero who found out the
names of his adversaries by means of a hair torn from his shin. An
identical procedure, consisting of throwing out magical darts, is also
used by Chortí elders who declare they "have shot the god-Seven" when
by magical art they succeed in making the Agrarian deity descend to
the center of the earth. A similar method is also mentioned in Mexican
sources which say that the sun, having come to a halt, was stung by a
mosquito in its leg. Ixtlilxóchitl says of this that
during the Third Age [equivalent to the Age in which the Popol Vuh places the invention of shooting out such magical darts], the sun
stood still for one full day without moving from its place; and as the
mosquito saw the sun so still and pensive, it said, "Lord of the
World, why are you so still and thoughtful and why don't you carry out
your duty as you are ordered? Do you want to destroy the world, as you
are now doing?" And seeing that the sun was silent and did not answer,
the mosquito approached and bit it on the leg. Feeling itself bitten,
the sun began to travel its usual course again.
In another version it is Citli who shoots an arrow at the sun but, the
arrow having missed its mark, the sun kills Citli.
(Esotericism of the Popol Vuh)