Means “work” in Japanese. This Emoji used to mean “open for business” and precedes business hours.
CJK Ideographs are characters used in Chinese, Japanese and Korean languages. Their writing systems all completely or partly use Chinese characters.
Japanese “Open for Business” Button was approved as part of Unicode 6.0 in 2010 under the name “Squared CJK Unified Ideograph-55b6” and added to Emoji 1.0 in 2015.