fief, allowance, pension, grant, happiness
祿 centers on a formal grant of resources that supports a person: a fief, allowance, pension, or similar provision. The happiness sense is the well-being that comes from receiving such support.
祿 combines 示 (altar, spirit) with 彔, which likely contributes the sound and may relate to carving or recording. The compound originally referred to blessings or official stipends granted by a ruler, seen as divine favor.
The left side 示 suggests a spiritual altar, and the right side 彔 looks like a hand holding a writing brush over a record. Picture a divine grant being recorded and handed down as a fief or pension.
For ロク, imagine a lord granting a fief while saying 'lock it in': lock -> ロク, and the grant is secured like a locked treasure.