In the second case, the hearer does not know a word's established sense. The sound reaches the ear, but the intended meaning cannot be obtained through that convention. The issue is more than a slightly lower degree of clarity: the necessary knowledge of the assignment is missing.
For instance, a listener unfamiliar with “layth” will not reliably identify the lion merely on hearing it. They might know “asad” and recognize the animal through that term, yet be unable to obtain the meaning through “layth.”
This distinguishes a meaning that is not conventionally accessible to this hearer from a known meaning reached through a longer inferential path. They are not the same kind of obscurity.