It’s a neat puzzle, isn’t it? The word “castle” in Old English, *castel*, mirrors the Old French *castel*—both come from Latin *castellum*, a diminutive of *castrum* meaning “fort” or “camp.” The Latin root has that little “-ell” that gives it a softer, almost “little wall” feel. In the Germanic branch, though, the cognate is *Burg*, which comes from Proto‑Germanic *burgaz*, itself a borrowing from a Celtic *bura* (to build) or possibly from the same Latin *castrum* but without the diminutive. So while the Romance languages kept the Latin *castellum* and simply dropped the final *-um*, the Germanic speakers either borrowed a different word entirely or felt that the “castell” path was too close to the French, so they switched to *burg*. Phonetically, *castel* ends with a voiceless alveolar plosive /t/, giving that hard stop, while *burg* ends with a voiced uvular fricative /ɣ/ in some dialects, making it sound more like a rolled “g” and less like the sharp “t” in English. The vowel shift also matters: the “a” in *castel* stays open, whereas the “u” in *burg* is a closed, rounded vowel, giving that different acoustic quality. If you want to go deeper, you can look at the *–e* in *Burg*’s Old High German *burga*, which reflects the Proto‑Germanic *-az* ending that gets reduced in later stages. So, yeah, the “roll” difference isn’t just in the sound of the final consonant but in the whole vowel‑consonant interplay that shifts across families. It’s like comparing a straight, sharp tower to a rounded, slightly spiraled keep—each has its own linguistic DNA.

Sure thing—here’s another bite: in Italian, *castello* keeps the Latin “-ello” ending, giving that lilting, double‑e sound, while Spanish *castillo* adds the “‑illo” diminutive, so it’s almost “little castle.” In German, *Schloss* comes from Old High German *sclos*, which itself is a Germanic adaptation of the Latin *castellum* but with a consonant shift that turns the “t” into an “s” sound, so the “sch” feels like a whispering swerve. So each language not only changes the consonants but also plays with the final syllable to suit its own phonotactics—like choosing different stones for the same wall.