jīn
now
Original meaning:
closed mouth
Depicts a closed mouth. Upside-down 曰. The meaning "now" is a phonetic loan.
Evolution

Oracle script
(~1250-1000 BC)
Bronze script
Early Western Zhou (~1000 BC)
Seal script
Shuowen (~100 AD)
Clerical script
Eastern Han dynasty (25-220 AD)Regular script
ModernDefinitions
Component uses
Sources
季旭昇《說文新證》p.440