lord, chief, master, main thing, principal
主 centers on the central or controlling figure: a lord, chief, or master, and by extension the main or principal thing.
(one's) master; (one's) employer; (one's) lord
head (of a household); proprietor (of a store); proprietress; landlord; landlady; master (of a servant)
head (of a household, etc.); leader; master
chief; main; principal; important
doctrine; rule; principle; -ism
claim; insistence; assertion; advocacy; emphasis; contention; opinion; tenet
protagonist; main character; hero; heroine
democracy; popular sovereignty
sponsorship (i.e. conducting under one's auspices); promotion; organizing; organising; hosting; staging
Democratic Party
head (of a household); proprietor (of a store); proprietress; landlord; landlady
starring (in a film, play, etc.); playing the leading part
chief; main; principal; major
independence; autonomy; self-reliance
housewife; mistress (of the house); homemaker
owner; proprietor; possessor (e.g. of talent, beauty, etc.)
main constituent; core; nucleus
leading part; leading actor; leading actress
(the) mainstream
shareholder; stockholder
leadership; initiative; spearhead
(pet) owner; keeper
Buddhist priest; bonze
person in charge; senior staff; manager; chief; head
主 originally depicted a lamp or torch with a flame above a stand, symbolizing the master of the house or the central figure. The modern form retains the dot above 王, though the historical connection to a lamp is not obvious from the current shape.
The dot above 王 looks like a crown or mark of authority over a king, making this the lord or master.
For シュ, imagine a shoe placed on the master's throne: shoe -> シュ, and the master sits above all.