con-: together, with
sist: derived from Latin "sistere", meaning "stand"
-ent: of doing something
So consistent means:
Of standing together.
- If some people stand together, their viewpoint or standpoint must be same. So one meaning of consistent is "behaving in the same way, or having the same opinions, standards, etc".
- If one person/thing's behavior stands together with before, it means "behaving in the same way over time".
Evolution of usage
Our target is of standing together.
Our target is consistent.