🔼The name Yom Kippur in the Bible
The name Yom Kippur doesn't really occur in the Bible, but rather Yom Kippurim (or even Yom Hakippurim). And as such it occurs only three times, namely in Leviticus 23:27 and 25:9 as יום הכפרים (yom hakippurim) and in Leviticus 23:28 as יום כפרים (yom kippurim).
Yom Kippur is the name of a holy day, namely the tenth day of the seventh month, which was to be regarded as a Sabbath upon which people were to humble themselves and offer fire to YHWH for their atonement. Every fifty years, sounding the ram's horn on Yom Kippur heralded in the year of Jubilee (Leviticus 25:10).
🔼Etymology of the name Yom Kippur
The name Yom Kippur obviously consists of two elements. The first word is the noun יום (yom), meaning day:
The second part of our name יום כפרים is the plural noun כפרים (kippurim), meaning atonement(s):
The letter ה (he) that sits in front of the kippurim-part twice out of three times, is either the definite article, or else a particle of motion. It's a very common occurrence in names of the form X-of-Y.
🔼Yom Kippur meaning
The name Yom Kippur means Day Of Atonement(s), but note that in the ransom business, it's highly unusual that an abductee has to cough up his own ransom. The choice of words of this name seems to suggest that the offering brought on Yom Kippur was not so much for one's own atonement but rather for the others.