Editing Openai/69186d20-2d14-8013-b9c6-c09000f173f6 (section)

=== Assistant: 2511141819ET ===
251114_1819ET

yeah, your reasoning is basically right in principle:

: 

but there are three big “but”s that blunt the observable effect.

===== Most of the obvious cognates you see across branches are just PIE common stock that everyone kept: =====
* ped- / foot
* tri- / three / trí
* new- / novus / nua
* gʷou- / bos / bó

That overwhelms everything.

Now suppose:
* PIE → Proto-Italo-Celtic for, say, a few centuries,
* then splits into Proto-Italic and Proto-Celtic.

In that narrow window, how much new lexical material gets created that:
# originates in Proto-Italo-Celtic (i.e. is an innovation relative to PIE), and
# survives in both Italic and Celtic, and
# is subsequently lost or replaced in Germanic and everyone else?

Answer: not necessarily very much, and a lot of it will be in semantic niches or later overwritten by contact/innovation.

So yes, you’d expect some extra shared retentions, but the denominator is enormous (thousands of PIE roots), and Italo-Celtic’s “own” layer is likely small and noisy. That’s why historical linguists lean heavily on systematic morphological and phonological innovations, where the signal-to-noise ratio is better.

===== Germanic↔Italic cognates look “obvious” to you because: =====
* Latin/Italian/French changes are fairly tame,
* Germanic changes (Grimm/Verner) are regular but you know them,
* the surface forms often stay transparently comparable.

Celtic, especially Goidelic, does things like:
* initial consonant loss and mutations,
* heavy vowel reduction,
* wholesale reshaping of clusters,
* reanalysis of old compounds into stems.

So a hypothetical Italo-Celtic lexeme might now look like:
* Lat X-Y-Z
* Ir something like CVC with mutations and weird broad/slender stuff

and your brain just doesn’t recognise it as related without doing full sound-law reconstruction. The “obvious cognate count” is massively biased against Celtic.

Corollary: even if there are extra Italo-Celtic shared retentions, they’re not going to look like neat foot/ped pairs to a casual modern eye.

===== You’re implicitly comparing (Celtic, Italic) vs Germanic, but in real history: =====
* Proto-Germanic sat geographically right next to Italic and Celtic in north-central Europe.
* There were early areal contacts Germanic↔Italic, Germanic↔Celtic, etc.
* Some of the “wow, Germanic and Latin match nicely” stuff is either deep IE retention or later areal/lexical convergence, not phylogenetic specialness.

So your lexicon is seeing:
* PIE retentions (everyone), plus
* early West-IE areal stock (Germanic–Italic–Celtic), plus
* your own familiarity bias (you know Latin and Germanic well), and then your System-1 is going: “Germanic and Latin are obviously close; where are all the Celtic friends?”

That’s not wrong as an impression, it’s just not aligned with how subgrouping evidence is actually evaluated.

===== Given a real Italo-Celtic stage, the hierarchy is roughly: =====
# Shared innovations in morphology and sound law - These must exist and are the primary evidence: superlative morphology, certain case/tense formations, particular sound changes. - This is what people cite when they argue “Italo-Celtic” at all.
# A smallish set of lexical isoglosses - A few roots that look like: PIE > Italo-Celtic innovation > survive only in Italic+Celtic. - But you don’t expect hundreds in the basic lexicon; you expect a handful and they’re often semantically shifted or obscure.
# No strong prediction about “feels like more cognates” - Because: - Celtic’s later phonology scrambles transparency, - Germanic–Italic contact adds spurious “extra closeness”, - and lexical replacement is fast and messy compared to morphology.

So: your conceptual point is right—a genuine subgroup should have some layer of extra shared retentions—but in practice that layer is small and heavily obscured, and doesn’t manifest as “I see more obvious cognates in my Duolingo vocab.”

If you want to go more rigorous, the next step would be: look at a published list of proposed Italo-Celtic lexical isoglosses, then separately at Italo-Germanic ones, and look at which branch of the tree those actually support once you control for PIE retentions and later contact. That’s the level where your retentions intuition can be made precise.