Are the two types of lustra distinguishable?

Question

One meaning of the word lustrum is a sacrifice for purification done every five years; another is a house of ill repute. I'd always figured that the two were complete homophones.

However, someone told me recently that the sacrifice has a long ū in its stem, while the debauchery has a short ŭ, which would be a convenient way to tell them apart.

Is this true? How can I check? My usual reference source is L&S, which unfortunately doesn't mark vowel quantity in closed syllables (…or even consistently in open ones); Wiktionary does show different vowel lengths, but I'm not sure where it gets that information from or how reliable it is.

Answer 1

My Latin-Dutch dictionary (Muller-Renkema, 1970) lists the debauchery, without the macron, as first lemma, saying it’s related to lŭtum, mud.

The sacrifice, with the macron, is related to lūstro, which in itself has two meanings.

1. illuminate, derived from a reconstructed form leuk-s-trom
2. purify, derived from a reconstructed form lŏu(e)s-trom cf. ἐ-λοϜεσ-σα vid. lăvo

I have no way of validating these reconstructed forms, but maybe this is something to go by.