ér
and
Original meaning:
beard
Originally a pictograph of a beard, now written as 耏. The current use as a conjunction is a phonetic loan.
Evolution

Bronze script
Late Western Zhou (~800 BC)
Seal script
Shuowen (~100 AD)
Clerical script
Western Jin dynasty (266-316 AD)Regular script
ModernDefinitions
ér
and; and then; and yet; but; as well as; and so; but (not); yet (not); (indicates causal relation); (indicates change of state); (indicates contrast)
Component uses
Meaning component in 1 character (0 verified)
Unknown component in 1 character (0 verified)
Sources