Our Gemara quotes Rav Huna, who makes an interesting curse against someone whom he saw violating chol Hamoed 

רַב הוּנָא שַׁמְעֵיהּ לְהָהוּא גַּבְרָא דְּקָא מְנַקַּר רִיחְיָא בְּחוּלָּא דְמוֹעֲדָא אֲמַר מַאן הַאי אִיתַּחִיל גּוּפֵיהּ דְּקָא מַחֵיל חוּלָּא דְּמוֹעֲדָא 

⁦The Gemara relates that Rav Huna once heard a certain man cutting grooves into his millstone on the intermediate days of a Festival. He said: Who is this? May his body be desecrated, for he desecrates the intermediate days of a Festival. 

The actual language of the curse was more of a play on words, actually I believe a three-way play on words. The person was using a mill on Chol Hamoed, thus he was desecrating mechallel Chol Hamoed. And, finally, the curse was that his body should be desecrated mechullal.

Let us analyze the etymology of this word חלל challal. Our mesechta deals with Chol Hamoed, which means the less-sacred days of Yom Tov. The meaning of Chol or challal seems to cluster around the idea of empty, which then leads to the opposite of holy, since something opposite of God is empty of His presence. That would seem to be the true meaning of Avraham’s appeal to Hashem (Bereishis 18:25):

חָלִ֨לָה לְּךָ֜ מֵעֲשֹׂ֣ת ׀ כַּדָּבָ֣ר הַזֶּ֗ה לְהָמִ֤ית צַדִּיק֙ עִם־רָשָׁ֔ע וְהָיָ֥ה כַצַּדִּ֖יק כָּרָשָׁ֑ע חָלִ֣לָה לָּ֔ךְ הֲשֹׁפֵט֙ כׇּל־הָאָ֔רֶץ לֹ֥א יַעֲשֶׂ֖ה מִשְׁפָּֽט׃

⁦It is profaning for You to do such a thing, to bring death upon the innocent as well as the guilty, so that innocent and guilty fare alike. It is profaning You! Shall not the Judge of all the earth deal justly?”

From there we also get the word corpse, since it is empty of life or a soul, as in (Devarim 21:1):

כִּי־יִמָּצֵ֣א חָלָ֗ל בָּאֲדָמָה֙

If a corpse is found on the earth

We also get the word flute, since it is a hollow cylinder (Melachim I:1:40)

וַיַּעֲל֤וּ כׇל־הָעָם֙ אַחֲרָ֔יו וְהָעָם֙ מְחַלְּלִ֣ים בַּחֲלִלִ֔ים

All the people then marched up behind him, playing on flutes.

And then a metaphoric use in Tehilim (119:22), which actually is laden with multiple meanings:

וְ֝לִבִּ֗י חָלַ֥ל בְּקִרְבִּֽי׃

My heart is empty inside. Or you can read it as my heart is profane, or my heart is dead.

By the way, according to some, Hebrew words can be broken down to a two letter root. And even more fascinating you can often see the pictographs meaning within the two letter root. So here the root, “ches lamed”, is made up a of the letter “ches” which is a pictograph for a wall. The letter “lamed” is the shepherd’s staff, which is the same root as to lead or teach because the shepherd leads the flock. The Avos were our shepherds and our teachers. Thus “ches-lamed” is to be led out of the wall of the home, that is to empty an occupied space.

Rav Huna’s curse was a play on words of Chol Hamoed, Chillul Moed, and that he is empty, profane or maybe even dead.

In general there seems to be a trend across cultures that curses, blessings and incantations rhyme or alliterate in some fashion. In the Song of the Witches in Shakespeare’s Macbeth:

Double, double toil and trouble;

Fire burn and caldron bubble.

Fillet of a fenny snake,

In the caldron boil and bake;

Eye of newt and toe of frog,

Wool of bat and tongue of dog,

Adder's fork and blind-worm's sting,

Lizard's leg and howlet's wing,

For a charm of powerful trouble,

Like a hell-broth boil and bubble.

 

Double, double toil and trouble;

Fire burn and caldron bubble.

Cool it with a baboon's blood,

Then the charm is firm and good.

And in the Torah, Noach blesses Yefes

יפת אלקים ליפת (בראשית ט:כז)

While several of Yaakov’s blessings have alliterations too:

יְהוּדָ֗ה אַתָּה֙ יוֹד֣וּךָ אַחֶ֔יךָ יָדְךָ֖ בְּעֹ֣רֶף אֹיְבֶ֑יךָ יִשְׁתַּחֲו֥וּ לְךָ֖ בְּנֵ֥י אָבִֽיךָ׃ שם מט:ח

גָּ֖ד גְּד֣וּד יְגוּדֶ֑נּוּ וְה֖וּא יָגֻ֥ד עָקֵֽב׃ שם:יט

Apparently there is an ancient human tradition that curses and blessings have more power when in some kind of rhyme or meter, and this would seem to be part of Rav Huna’s intention.

The question is, why does it help? I will share two thoughts:

1. Since in l’shon kodesh words that sound the same are often related in meaning, as we clearly saw with challal, tapping into the commonality of words intensifies the power. It creates a harmonic resonance that amplifies the effect.
2. The repetition of similar words allows the person to enter into a trance, which channels spiritual energies and focus.

Though stemming from different reasons, both psychologists and mystics will agree that words have a special power.