(sh, Shellish). The original command-line interpreter shell and script language for Unix written by S.R. Bourne of Bell Laboratories in 1978. sh has been superseded for interactive use by the Berkeley C shell, csh but still widely used for writing shell scripts.
There were even earlier shells, see glob. [Details?]
ash is a Bourne Shell clone.
["Unix Time-Sharing System: The Unix Shell", S.R. Bourne, Bell Sys Tech J 57(6):1971-1990 (Jul 1978)].