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

=== Assistant: 2511132219ET ===
251113_2219ET

exec:
* Lenition = originally purely phonetic weakening in certain positions (between vowels, after vowels, etc.), later “frozen” and turned into a grammatical marker.
* Eclipsis = originally from nasal + stop clusters created by endings/prepositions; nasals got absorbed and only the “eclipsing” consonant survived as a phonological trace, then reanalyzed as a grammatical alternation.

I’ll keep it compact but precise.

==== Both systems follow the same general historical path: ====
# Normal phonetics / sandhi: sounds change predictably in certain environments.
# Morphology erodes: endings and prepositions that created those environments shrink or vanish.
# But the sound alternations survive, so speakers start treating them as morphological exponents (like case/tense markers) rather than just “lazy pronunciation”.

Irish is a textbook case of this: old endings → lost; mutations remain.

==== ### ====
* Indo-European languages often weaken voiceless stops between vowels, or after vowels.
* Celtic took this quite far: intervocalic /p t k/ → fricatives or approximants, and similar for voiced ones.

Very simplified pathway:
* VCV → V ɸ / θ / x V (or their voiced counterparts)
* Over time: these fricatives sometimes voiced, merged, or disappeared.
* Emotional/conversational weakening after function words (like particles, prepositions, possessives) was very common.

So originally, the difference was purely phonetic:
* …V + C… vs …V + V-C… → consonant sounded “softer” in the latter, because it was in an intervocalic-like environment.

===== By Old Irish (c. 700–900 CE): =====
* Many inflectional endings had been lost or heavily reduced.
* But the consonant alternations remained very salient and systematic: - “soft” vs “hard” versions after certain particles, in certain morphological contexts.
* Speakers generalized this: >

So lenition became:
* Phonological: a contrast between “fortis” stop and “lenis” fricative approximant.
* Morphological: marks gender, case, tense, possession, etc. depending on context (exact pattern fossilized from earlier morphosyntax).

===== All that gets regularized and re-spelled: =====
* Old dot above (ḃ ċ ḋ …) → modern bh ch dh ….
* The triggers (possessives, articles, past particles, etc.) reflect where lost endings and old prepositions once created leniting environments.

So: lenition is fossilized intervocalic/ postvocalic weakening that turned into overt grammar.

==== ### ====

Eclipsis patterns like:
* mb, nd, ŋg, bhf, etc. are exactly what you get when a nasal consonant comes into contact with a following stop/fricative.

For example (schematic):
'' ''n + b → [mb]
'' ''n + d → [nd]
'' ''n + g → [ŋg]

This arose from:
* nasal-final prefixes / prepositions / particles / endings colliding with word-initial consonants.

Think:
* “in the X”, “our X”, “of the X (plural)”, “that/which X” where the preposition/pronoun/particle had a nasal at the end.

===== Then familiar story: =====
* The original nasal segments and vowels shrink or disappear; boundaries blur.
* But mb, nd, ŋg, bhf, bp, dt… survive as the surface cue that there used to be a nasal / ending / preposition there.

So what was originally:

: 

becomes reanalyzed as:

: 

The underlying consonant (b, c, d, …) is kept in the spelling but mostly not pronounced, because historically it was the second member of the cluster.

===== Now, eclipsis is: =====
* Triggered by elements that historically involved a nasal or ended in nasal consonants: - ár, bhur, a (their) (from older forms with nasal components), - i + an → sa/san, sna, na (gen. pl.) in some uses, - certain numbers and relatives/complementizers.
* Spelled as mb, gc, nd, bhf, ng, bp, dt, n-.
* Pronounced as the nasalized/voiced first letter, with the original initial mostly silent or reduced.

So eclipsis is fossilized sandhi with a preceding nasal, turned into morphological marking.

==== Crucial point: the spelling system is conservative and tries to: ====
* Preserve the original root,
* Show the mutation type as an extra layer (h for lenition, extra consonant for eclipsis).

Historically, consonant gradation was:
* Phonetics: predictable allophony from context.
* Diachronic change + erosion: context disappears → allophony becomes contrastive.
* Orthography + standardization: systemized as lenition vs eclipsis with clean rules.

This is very similar to how, say, Grimm’s Law changes turned into regular morphological alternations in Germanic, except Irish decided to keep both sides of the alternation in spelling and give them syntactic jobs.

==== - Lenition = “used to be between vowels / after vowels / in weak position; stop weakened → fricative or /h/ or zero; now used as a grammar marker.” ====
* Eclipsis = “used to follow a nasal from an ending/particle; cluster N+stop → mb/nd/ŋg etc.; nasal part was originally from the preceding morpheme; now the cluster itself is a grammar marker.”

If you want to go nerd-deep next, we can pick one specific pattern (e.g. possessive pronouns or the preposition “in”) and trace its Old Irish forms → sound changes → modern lenition/eclipsis triggers, step by step.