The masoretic text is, Isaiah 61:6
וְאַתֶּ֗ם כֹּהֲנֵ֤י יְהֹוָה֙ תִּקָּרֵ֔אוּ מְשָׁרְתֵ֣י אֱלֹהֵ֔ינוּ יֵאָמֵ֖ר לָכֶ֑ם חֵ֤יל גּוֹיִם֙ תֹּאכֵ֔לוּ וּבִכְבוֹדָ֖ם תִּתְיַמָּֽרוּ
and for Isaiah 66:12
כִּי־כֹ֣ה ׀ אָמַ֣ר יְהֹוָ֗ה הִנְנִ֣י נֹטֶֽה־אֵ֠לֶ֠יהָ כְּנָהָ֨ר שָׁל֜וֹם וּכְנַ֧חַל שׁוֹטֵ֛ף כְּב֥וֹד גּוֹיִ֖ם וִֽינַקְתֶּ֑ם עַל־צַד֙ תִּנָּשֵׂ֔אוּ וְעַל־בִּרְכַּ֖יִם תְּשׇׁעֳשָֽׁעוּ
So in both of these verses the word that your translation translates as "glory" is כבוד (vocalized like kavod in American English).
In Isaiah 61:6, kavod is in a compound word ובכבודם where the first letter, ו (vav) is the conjunction "and", the second letter, ב (beth) is the preposition "in", and the last letter, ם (mem) is the third person plural possessive, "their".
In Isaiah 66:12, kavod is not in compound form but is in adjacent form with the following word goyim, nations, that indicates which kavod. That is, the kavod of the nations.
kavod is a masculine gender noun used in the sense of
depending on the context. It has the same trigram root כבד as kaved, an adjective meaning heavy, weighty, grave, severe or a lot of something, and kibed, a verb meaning to honor or to respect. These words appear many times in the OT.
Note that the modern English translations sometimes use "riches", "honor" or "splendor" as well as "glory" in Isaiah 61:6. All of these are meanings that are conveyed by the word kavod in this verse. Since a translator is limited to a single-word translation, he needs to choose what appears to him to be the primary sense in context. The language of this chapter is poetic and figurative. No translation can nail it down. From the context of the previous verses that deals with rebuilding the ruins and the service of the nations, I think that kavod in this verse means the wealth for which the nations are respected.
Many of the modern English translations use "wealth" or "riches" for kavod in Isaiah 66:12. One, Young's Literal Translation, uses "honor". My feel for the verse is that kavod is used in the sense of "the respect of".
In any event, I would caution against deciding that you have understood the verse based on the English meaning of a single translation's word choice. In particular, I would advise against trying to read some theological concept or symbolic meaning into kavod in these two verses. The verses in manuscript do not support this.
On a side note, I noticed that some translations use "Gentiles" for "goyim" in both of these verses. I think that this is a mistake, as the intent, phrased in modern English, is not "non-Jews" but "the peoples of the world".