Alien and Aliens take place on LV-426, Prometheus on LV-223. What does "LV" stand for?
There are no canon sources explaining the planetary designations used in the Alien franchises. Indeed, there does not even seem to be a planetary designation system in place at all. LV-426 was barely used in the script of the original Alien with the planet's name being Acheron.
There was barely any connection to the two names and only in later materials were the two ever mentioned together. The later movies, books, games and now finally Prometheus mention only a few other planets with this designation system including LV-233 and LV-1201.
LV-426 was first introduced in the 1979 film Alien, though it is not named and is simply referred to as a "planetoid" or "ball". In the 1986 sequel Aliens, LV-426 is named. On the timeline of the official viral website for Weyland Industries, as part of the promotion for the film Prometheus, the planet's name appears on the timeline page, as officially "Acheron LV-426" bringing both names together. The planet was thought to appear in the film, but instead, the planet LV-223 was used. --Alien versus Predator Wiki > Archeron LV-426
LV is you look at it from a Nasa Stand point means launch Vehicle which is simple a vehicle that makes a landing on the surface of a planet, delivering some payload
Could be simply that launch Vehicle 426 landed on that planet and on its payload was device to classify the planet, Thinking on this it could be said they when there able to map out, entire parts of the universe, each planet wont have a name like Earth Mars Venus etc, they would simply give it a number value for easy classification and data basing
It could simple be Level 426 or level 223 LV223 - near Earth atmosphere, where DNA-identical beings reside LV426 - sub-zero, rocky, windy environment with inhospitable atmosphere
A level Based on the level of terraforming the planet has done naturally or by force on what number vaulue i cant find, but closer to 0 would be Perfect earth maybe? and farther away from earths score of 0 is inhospitable?
Similar to the in-depth analysis done by the Prometheus movie in their relation with LV-223, I've looked up Leviticus Book 4 chapter 26, which the first part is about rituals of some sort (because Leviticus is mainly an instructional section), and the quote I gleamed from that section was this "In this way the priest will make atonement for the leader’s sin, and he will be forgiven." This could reference Ripley in a way, or any other protagonist in the movies related to the Alien Franchise, in which it's usually a subordinate or person not in charge who solves the problem caused by the one in charge. It's usually the pride and doings of the person in charge (the Company, Weyland himself, a member of his family or android copy of him) that cause these problems, and it takes one driven individual to fix them. The first part of chapter 26 says something about "He must burn the fat at the alter to make an offering." This can have the meaning that they take the thing desired, usually the xenomorphs themselves (although sometimes Predator technology is the goal), or the knowledge of the Engineers or such, and destroy it, and thus the "sins will be forgiven," or in other terms "everything becomes hunky-dory." Burning an offering seemed to be a way to deliver it to God (or gods depending on which religion made an offering, but since Leviticus is a text in the Hebrew scriptures and therefore Christian and Muslim texts, though barely anyone follows the entire thing, but for the sake of that I'm using Monotheism as the main example), and fire is a repeated way in which the things others want is attempted to be destroyed and actually is. Flamethrowers, massive explosions, and molten metal are used as ways to try and destroy the "offerings," or xenomorphs, and often succeeds. This is my analysis of it, though the writers could have had something completely different in mind.