Right, since not all underwear is lingerie, as described in the wiki. We could also add panties -> underwear implication, and bra -> underwear, I guess. Ah, it seems there's already bra -> lingerie. That doesn't really make sense, though.
Last I paid any attention to that, that whole group is pretty natty (it's one of the older ones). As I recall it, we were originally using lingerie for things that weren't panties, but underthings ended up being more complicated than expected.
Although...are nighties, camis, chemise, et al really underwear? When I think "underwear", I for some reason have a more utilitarian connotation attached to it.