Linguistic curiosity

A usual Saturday. Studying the map of the Ooppera building I became cursious why "lämpiö" ("the Foyer" in English) is lämpiö and nothing else. We started to discuss it and we involved some of the Oooppera employees in our discussion. Our common hypothesis in the end was that it has something to do with "lämmin". Probably, halls in operas and theaters were not warmed in old times and only the foyers were heated. Probably it is warm because it is crowded and some beverages are served there. Who knows? Google does not know.

So, two main conclusions:
Conclusion 1. Linguistic discussions can be a start for a small talk.
Conclusion 2. Not every word in Finnish is that easily googlable.