-NL- and -LL- in Classical Latin

Question

I just stumbled upon an old meta question about the name of our chat room, and a comment gave me the impression that the classical spelling would be conloquium rather than colloquium. (Let me ignore capitalization and comparing U and V in this question.) In cases like this, are both NL and LL used in classical Latin, or is one preferred over the other?

How do we know? It seems likely to me that later copyists would have changed such spelling details, so classical choices would only be visible in inscriptions — but this is only my guess.

If you have evidence for other similar cases of assimilation and can argue that NL/LL should behave the same, that is perfectly acceptable. The main interest of this question is more focused, but more general arguments are welcome. Notice that this question is about spelling, not pronunciation.

Answer 1

Check out the Epigraphic Database Heidelberg. It thankfully allows you to search words, which will allow you to look at deeper results. From a cursory search, though it seems that conl- is earlier, but by the Augustan Age, both were frequently used.:

• For conl: note that Sulla's inscription in Delos has conlegia and conlata. It's early and frequent, even when coll- is also used.
• For coll: Aside from Collina and colle (neither of which were formed from cum + root; see de Vaan p. 124-125), you have what seems to be Collegium in an inscription in the late Republic/early Empire and a definite attestation in 17 BCE. From there you see it freely.

Decided to take a look at inl-/ill-, too, and same thing:

• inl-: Early, frequent.

• ill-: First one I found was from post-Augustan Spain. Very infrequent.

Further searches show that conloquium is attested relatively early, but you don't get colloquium until 226 CE.

Answer 2

It seems the frequency of the assimilation -NL- > -LL- may depend on the word. Hale and Buck's Latin Grammar (first published 1903) says

spellings like adferō, adsignō, conlocō, etc., prevailed to the almost total exclusion of afferiō, assignō, collocō until several centuries after Christ, so that we must believe that ad and con were actually so pronounced in such words. Yet [...] the spelling conlēgium, exclusively employed down to the time of Augustus, gives way to collēgium in the Augustan period, though conlocō and other similar forms continue to prevail until a much later period.

(p. 24)

The next page gives the following summary for the use of con-l- vs. col-l-:

Before l, the unassimilated form is preferable except in col-ligo and its compounds, e.g. con-locō, con-loquium, con-lāpsus, etc.

(p. 25)

Cser (2016) argues that the high rate of assimilation in colligo arose from its frequency ("Aspects of the Phonology and Morphology of Classical Latin", Figure 36, p. 173).