[Mikhail_Edoshin]

Light year is not just a name; year is a natural length of time and light speed is also a natural constant. The whole unit is natural and is based on things that make sense on such distances. This is same for all natural units; they grew up from usage. (This resulted in things that appears illogical, like having different with similar name for different applications, but this is only appearance. We measure water differently from oil or precious drugs and differently when we cook with water or build a dam, so it makes all the sense to have different units for different purposes.)

Meters, however, have a different story; the meter was invented by some French scientist about the time they were changing everything after the revolution, including month names; somehow month names reverted back to normal, but meters stayed. The meter was initially defined as 1/40,000,000 of the length of a meridian. Here only the length of the meridian is natural to some extent, although I fail to see how it is relevant to what is normally measured with meters, and the constant is completely artificial.