"Rembrandt" is a modification of the spelling of the artist's first name that he introduced in 1633. Roughly speaking, his earliest signatures (ca. 1625) consisted of an initial "R", or the monogram "RH" (for Rembrant Harmenszoon; i.e. "Rembrant, the son of Harmen"), and starting in 1629, "RHL" (the "L" stood, presumably, for Leiden). In 1632, he used this monogram early in the year, then added his patronymic to it, "RHL-van Rijn", but replaced this form in that same year and began using his first name alone with its original spelling, "Rembrant".
In 1633 he added a "d", and maintained this form consistently from then on, proving that this minor change had a meaning for him (whatever it might have been). This change is purely visual; it does not change the way his name is pronounced. Curiously enough, despite the large number of paintings and etchings signed with this modified first name, most of their documents that mentioned him during his lifetime retained the original "Rembrant" spelling.
