surname Zhou; Zhou Dynasty (1046–256 BC)
Depicts a carved jade object, now written as 彫/琱. The meaning later shifted to "circumference" and "cycle". Later the 口 component was added when 周 was used to refer to a geographical region to indicate that the character was only "mouthed", i.e. used for its sound. In simplified Chinese 周 is also used to mean "week", while in traditional Chinese this meaning is written with a separate character 週.
《說文》：“周，密也。从用、口。，古文周字从古文及。”
to carve jade