The word is Aramaic (ממון in Hebrew script) and means something like "wealth". μαμωνᾶς is simply the Greek transliteration of the Aramaic word. Here is Jastrow's entry for it:
It appears throughout the Targumim - Aramaic translations/paraphrases of the Hebrew Scriptures written in Aramaic script. The Greek word appears only 4 times in the New Testament (in the Gospels of Matthew and Luke), but not at all in the Septuagint, suggesting that it does not relate to any pure Hebrew word. Augustine (Our Lord's Sermon on the Mount II.14) had speculated that the word was either Carthaginian ("Punic") or "of the Hebrews", while Jerome thought the word was from the "Syrians" (Letter XXII) - both somewhat on the mark.
From what I can determine, these are some of the occurrences in the Targum:
Exodus 15:9 (Cairo Geniza Targumic Fragment MS G)
דַּהֲוָה אַמָר סַנְאָה אֶרְּדֹּוף אַדבִיק בִתקֹוף יְדִי אֵפַלִּיג
בִזְּתָא מָמֹונָא וּכְסֹותָא ומָן דִכְסָף וְמָן דִּדְהַב לְהַעֲדִי
תִשְׂבָע מנּהֹון נַפשִי כַד אַקִּיף עְָלֵיהֹון בְחֵילֵי וְבִגְדֹודִי
אֶשלֹוף חַרבִי תְשִיצָנּוּן יְדִי
The enemy said, ‘I will pursue, I will overtake, I will divide the spoil, my desire shall have its fill of them. I will draw
my sword, my hand shall destroy them.’
Exodus 18:21 (Targum Neofiti)
ואת תחמי מכל עמא גברין גברי חיל דחלין מן קדם ייי גברין קושטנין סניין
ממונא דשיקרא ותשוי עליהון רברבני אלפין ורברבני מאוון ורברבני חמשן
ורברבני עשרה׃
Moreover choose able men from all the people, such as fear God, men who are trustworthy and who hate a bribe; and place such men over
the people as rulers of thousands, of hundreds, of fifties, and of
tens.
1 Chronicles 26:24 (Codex Urbaniti/Targum Chronicles)
ושבואל הוא יונתן בר גרשם בר משה תב לדחלתא דייי וכד חמא דוד דהוה מתבהיל
על ממונא מנייה נגידא על תסבריא׃
And Shebuel the son of Gershom, son of Moses, was chief officer in charge of the treasuries.
Jeremiah 22:17 (Mikraot Gedolot HaKeter edition/Targum Jonathan to the Prophets)
אֲרֵי לֵית עֵינָך וְלִיבָך אֲלָהֵין עַל מָמֹונָא לְמֵינַס וְעַל דַם
זַכַי לְמִשפַך וְעַל עֻשקָא וְעַל דְבִרעוּת נַפשָך לְמַעֲבַד׃
But you have eyes and heart only for your dishonest gain, for shedding innocent blood, and for practicing oppression and
violence.
I understand that these are translations out of the Masoretic Text (I show the RSV), so I am making some assumptions about what matches what is in the Targum.
I have no idea how to determine whether the word is used in any secular Aramaic/Syriac works that have been written. I also searched the Perseus search engine and found absolutely no use of the Greek transliteration in any secular Greek works.
