This lead me down a short Wikipedia rabbit-hole that is quite interesting (at least to me). Apparently Dutch originally had "du" as 2nd person singular and "gi

This lead me down a short Wikipedia rabbit-hole that is quite interesting (at least to me). Apparently Dutch originally had "du" as 2nd person singular and "gij" as 2nd person plural. From the 16th century, "gij" started being used as singular polite form. (Possibly under the influence of Latin and French.) Later, "du" disappeared. Up to this point, the progression is similar to English. "gij" then transformed to "jij" in the northern part of the Dutch language area and in written language; while it remained "gij" in Flemish spoken language. However, then in the 17th century people started using "Uwe Edelheit" ("Your Nobility") as a new formal form in letters. This evolved into the current formal pronoun "u". (Note also that the accusative form of "gij" is also "u", but is not related to the formal "u".) Sources: https://nl.wikipedia.org/wiki/Gij https://nl.wikipedia.org/wiki/Gij, https://etymologiebank.nl/trefwoord/gij https://etymologiebank.nl/trefwoord/gij, https://nl.wikipedia.org/wiki/U_(voornaamwoord) https://nl.wikipedia.org/wiki/U_(voornaamwoord), https://etymologiebank.nl/trefwoord/u https://etymologiebank.nl/trefwoord/u