Hendrick Croeger's middle name

A document dated 27 April 1652 gives Hendrik Kroeger's name as "Hendrick Evertsz Croeger". I have not seen his middle name, Evertszoon, mentioned before. This sort of name is usually abbreviated down to Evertsz (ommitting the period that we would put there, writing "Evertsz."). You might also see names like this called Evertssen, although it could be Evertsen, like the famous Zeeland family. By the way, Hendrick Kroeger commanded the convoyer Marcus Curtius (24 guns) up until 22 July 1652, when the English attacked the fishing protection squadron, of which the Marcus Curtius was part. He commanded the ship Leiden (28 guns) during 1653.