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

===== The Italo-Celtic business is about shared ''derived'' features that other IE branches don’t have, for example (schematically): =====
* Superlative morphology built on a common -isamo- type pattern (Latin -issimus, Old Irish endings from the same template).
* Parallel developments in certain case endings and verb tenses/moods, where Latin and Celtic show the same weird reshaping and others don’t.
* Some specific sound changes and lexical isoglosses that look like common innovations, not just inherited PIE.

Those are the things that push Celtic and Italic together higher up the tree. They’re buried in paradigms and reconstructions, not in transparent modern words.

So:
* Germanic–Italic: tons of obvious cognates because you know both families well, but nearly all are just “shared PIE roots + regular sound changes.”
* Celtic–Italic: fewer visibly similar modern words to your eye, but more shared weird morphology that looks like it happened once and was then inherited by both.