🔼The name Kiyyun in the Bible
It's not clear whether the name Kiyyun (or Chiun) actually appears in the Bible, but if it does, it does so in Amos 5:26. It's not wholly clear what the prophet is trying to convey in that verse, but one possibility is that he's successfully conveying a lot of things at once, which is of course nothing short of brilliant.
Amos is talking about Israel's forty years of wandering, when he refers to something that doesn't seem to be incorporated in the Torah (which is the part of the Bible that contains the Exodus), namely that on their trek to Canaan, the Israelites carried several idols along with them. In this single little sentence, Amos manages to refer to the gods Sikkuth, Moloch, Kiyyun, Selem, the Heavenly Host and perhaps also Asher and El:
This complicated accusation is hard to translate one way or the other and the versions vary considerably. Allowing for variations in spelling, the NAS, JSP and Young Translations speak of "Sikkuth your king and Kiyyun, your images"; the KJV and Darby have "the tabernacle of your Moloch and Kiyyun your images," and the NIV and ASV have "the shrine of your king, the pedestal of your idols".
Matters are made even more complicated by Stephen's quote of Amos 5:26 as it occurs in the Septuagint, by which he speaks of "the tabernacle of Moloch and the star of your god Rompha" (Acts 7:43). Scholars used to think that truth could only be conveyed by accuracy but have since then long concluded that it's the other way around: perfect accuracy does not occur in nature and is therefore false.
The operating mechanism of Truth (and thus the Bible) allows for considerable variation between source text and interpretation (read our article on the name Masoretes), and Stephen's quote in Acts does not necessarily reflect the one and only true interpretation of Amos 5:26. Just the one that was relevant for Stephen at that time.
🔼Etymology of the name Kiyyun
If Kiyyun is a name, it's probably the name of a Babylonian and Assyrian god known as Kaiwanu (which was also known as Sak-kut, hence probably the reference to Sikkuth). This Kaiwanu was apparently the planet we call Saturn (according to William Rainy Harper's A Critical and Exegetical Commentary on Amos and Hosea).
Amos may just simply have wanted to transliterate the name of the deity the way it sounded to him back then, but the way it turned out in Hebrew makes it seem that it was a diminutive (hence the final ון, which doesn't make smaller, but rather localizes or personifies) of the word כי, and that word already existed in Hebrew:
Of course, the word כיון as derived from כי doesn't occur anywhere in the Bible, which suggests that it didn't exist. But a Hebrew audience might have associated our name with it anyway, or else with the verb כון (kun), meaning to be established, fixed, certain, etcetera:
Apart from what it might have meant originally in Assyrian, to the Hebrews the name Kiyyun probably meant The Established One, and may have rivaled אלהי אמן (e'lhy 'mn), or the God of Amen of whom the prophet Isaiah speaks (Isaiah 65:16).
Technically, the name Kiyyun could also be construed as כי plus ון and mean a rather contrived Likeness or Thatness or He Why, which brings this name in close vicinity with the most likely meaning of the name YHWH.
If Kiyyun is not considered to be a name, then the translation of Pedestal, from the verb כון (kun), seems most warranted.