This is the Chinese character for etermity. This character is significant especially for Chinese calligraphy as it encapsulates all the eight possible brushstrokes found in the Chinese language. These eight are collectively referred to as the Eight Principles of Yong. It is known in Korean as 영자팔법 (yeongjapalbeop).
The above is my favorite example of this type of calligraphy (the Korean manifestation). The name is Buiseonrando (불이선란도), which was written and painted by 김정희 (Kim Jeonghee), who lived from 1786-1856.