Initially referred to as the Samsung Gear S4, rumours then suggested it might be called the Samsung Galaxy Watch, codenamed Galileo. This has seemingly been confirmed by the FCC - the US Federal Communications Commission - who also have details on two different Galaxy Watch devices.
The FCC doesn't give us a lot of information on the devices, only enough to show where the regulatory text will be placed and what radio communications standards they use - LTE, Bluetooth, Wi-Fi etc. The confirmation of LTE suggests that Samsung will be offering some versions of the Galaxy Watch that will have their own connection, providing online services without the need for a smartphone.
The smaller Samsung Galaxy Watch is said to measure 51.2mm x 43.4mm with a 1.19-inch display. The larger Samsung Galaxy Watch is said to expand to 48mm according to Droid Life who uncovered the details and compared the two side-by-side, with a larger 1.3-inch display.
Rumours have suggested that the Galaxy Watch will be unveiled alongside the Samsung Galaxy Note 9 launching on 9 August. This hasn't been confirmed by Samsung so there's still a chance it could launch at IFA 2018 later in the month.