Difference between "immergo" and "summergo"

Question

In Spanish we have the verb sumergir, coming from Latin:

sum-mergo (subm-), si, sum, 3, v. a.,

I. to dip or plunge under, to sink, overwhelm, submerge, submerse.

Nonetheless, some related word such as inmersión and inmerso come from a similar Latin verb:

immergo (inm-), si, sum, 3 (

I. perf. sync. immersti, Plaut. Bacch. 4, 4, 26; acc. to the second conj., inf. pres. pass. immergeri, Col. 5, 9, 3), v. a. in-mergo, to dip, plunge, sink, or stick into any thing, to immerse (mostly poet. and in post-Aug. prose).

The definitions for both verbs are quite similar, but only the summergo verb reached the Spanish language as sumergir. There were attempts to stablish an inmergir verb but the Royal Spanish Academy stated that such verb was pointless in the Spanish language.

So, we have sumergir but not inmergir and I'm trying to understand why. I see in the definition for immergo that that verb was mostly used in poetry. So was it a cultured word and hence less used? Was in fact the verb summergo most used in Latin than immergo with the meaning of to dip, plunge or sink?

Answer 1

As you mention, Lewis and Short say that immergō was "mostly poet[ic] and in post-Aug[ustan] prose". Whitaker marks its frequency with a C, which means between 5 and 20 citations were found in his corpus.

On the other hand, L&S say that submergō was "class[ical]; most freq[uently] pass[ive]". Whitaker marks both submergō and summergō with a C, giving them separate entries, which may or may not actually mean it's more common.

It's also worth noting that English has verbs from the frequentitive forms "immerse" and "submerse", and a verb "submerge", but no *"immerge" (at least not that I've ever heard as a native speaker). This hints that submergō's descendant was more popular in the Norman French that affected English.

From this, I'd take away that submergō was the common classical form, while immergō started off as a poetic word and got somewhat more popular later on. Submergō was always more common, and is the form that got better-established in Spanish and English, while immergō remained rarer; however, both have descendants in many Romance languages, so one never fully displaced the other.

(P.S. As a linguist, I wouldn't trust the Spanish Academy to determine what's a "real word" and what isn't. Mitomino's answer points out that inmerger was used by Benito Pérez Galdós, a novelist often compared to Dickens and Tolstoy, and Santiago Ramón y Cajal, a Nobel prize winner. I'd take their testimony as native speakers over the Academy's prescription any day. It might be archaic or outdated, but it seems to be a real word.)

Answer 2

Both verbs do exist in Catalan: immergir and submergir (vid. https://dlc.iec.cat/). Immergir: "ficar dins un líquid" ('to introduce into a liquid') / Submergir: "Posar sota l’aigua o altre líquid" ('to put under the water or other liquid").

As for Spanish, I've seen that inmergir is found in authors like Ramón y Cajal o Pérez Galdós. Vid. https://twitter.com/RAEinforma/status/648450561776427008 According to RAE (Real Academia Española), "[su uso] sería raro, pero perfectamente correcto" ('[its use] would be odd, but perfectly correct'). So feel free to use both verbs!