Aeonian and Hard core

Aeonian adjective - Of or relating to a geological eon (longer than an era).

Hard core and aeonian are semantically related. In some cases you can use "Hard core" instead an adjective "Aeonian".

Hard core noun - The most dedicated and intensely loyal nucleus of a group or movement.

Aeonian and hard core are semantically related. Sometimes you can use "Aeonian" instead an adjective phrase "Hard core".