Vistula.

In the form Visula and Visla at least sometimes directly acquired from Proto-Slavic *Visъla. The form Viscla resolves the /sl/ cluster like in Sclavus, uncommon in Latin, and in Germanic, via which it has sometimes been acquired. Often explained as from the Proto-Indo-European root *weys- (“to flow”) as in Proto-Germanic *waisǭ (“mire”), although if of Slavic origin then *visěti (“to hang”) would afford a readier stem, suffixed + *-lo + *-a or + *-sla, for which ever reason they would have called it the “hanging river” or “saggy stream”. Considering how both the Germanic and Baltic cognates clearly shows a long vowel, it is not impossible it may have one in Latin as well, which however cannot be ascertained, as it is hidden quantity.