Why are elements of a projective Hilbert space called "rays" instead of "lines"?

Question

The elements of a projective Hilbert space are usually called "rays". But they're isomorphic to one-dimensional subspaces of the Hilbert space (which are in turn isomorphic to the field $\mathbb{C}$). It seems to me that the word "line" makes a much more natural analogy for a one-dimensional vector space or a field than the word "ray" (although neither analogy is perfect, since the field is the complex rather than real numbers). Is there any motivation for this confusing nomenclature, or is it just a historical accident?