The only example I remember of interpreting the Hebrew letters comes in the Talmud Shabbos 104a. Here is the beginning of the first exposition (please read the rest from the link).
The Sages said to Rabbi Yehoshua ben Levi: Young students came today
to the study hall and said things the likes of which were not said
even in the days of Joshua bin Nun. These children who only knew the
Hebrew alphabet interpreted the letters homiletically.
Alef beit means learn [elaf] the wisdom [bina] of the Torah. Gimmel
dalet means give to the poor [gemol dalim]. Why is the leg of the
gimmel extended toward the dalet? Because it is the manner of one who
bestows loving-kindness to pursue the poor. And why is the leg of the
dalet extended toward the gimmel? It is so that a poor person will
make himself available to him who wants to give him charity. And why
does the dalet face away from the gimmel? It is to teach that one
should give charity discreetly so that the poor person will not be
embarrassed by him.
The thought is an understanding of the Hebrew alphabet but not a key to interpreting the letters in different words.
Later on in the same passage, the letters are interpreted in a different way:
The Gemara cites another midrash that also deals with the letters of
the alphabet. This one uses a code in which the first letter is paired
with the last letter, the second letter with the penultimate one, and
so on [alef tav, beit shin]. Alef tav, God said: If he despised Me
[oti ti’ev] would I desire [etaveh] him? Beit shin: If he does not
desire to worship Me [bi], shall My name [shemi] rest upon him? Gimmel
reish: He defiled his body [gufo]; shall I have mercy [araḥem] on him?
The word comprised of the letters gimmel and reish in Aramaic means
licentiousness. Dalet kuf: He locked My doors [daltotai], shall I not
cut off his horns [karnav]? To this point, the Gemara interpreted the
letters as referring to the attribute of the wicked.
However, with regard to the attribute of the righteous it is taught
differently. Alef tav, beit shin: If you have shame [ata bosh], gimmel
reish, dalet kuf: If you do so, you will reside [gur] in the heavens
[bedok], as the verse says: “Who stretches out the Heavens like a
curtain [dok]” (Isaiah 40:22). Heh tzadi, vav peh: There is a
partition [ḥatzitza havei] between you and anger [af]. Zayin ayin, ḥet
samekh, tet nun: And you will not be shaken [mizdaze’a] by the Satan.
Yod mem, kaf lamed: The minister of Gehenna said before the Holy One,
Blessed be He: Master of the Universe, send the righteous as well into
the sea to which all go [yam kol], Gehenna.
(see the link for more examples.) Again this does not provide an interpretative tool for use generally.