roof, house, shop, dealer, seller
屋 centers on a covered structure: a roof, a house, or a place of business like a shop. The dealer/seller sense extends naturally from the idea of a shop or establishment.
屋 combines 尸 (a roof or building) with 至, which likely contributes the sound. The character originally referred to a roof or dwelling.
The outer 尸 is like a roof, and inside is 至, which looks like a person arriving. Picture arriving at a house with a roof: 屋 is a roof, house, or shop.
For オク, imagine an oak tree growing right through the roof of a house: oak -> オク, and the house still stands.
room; chamber
Nagoya (city)
roof
izakaya; tavern, bar, etc. that also serves various dishes and snacks
residence; estate; grounds; premises; mansion
hut; cabin; shed; (animal) pen
bookstore; bookshop
rooftop
cart (esp. a food cart); stall; stand
outdoors; outside
indoors
house; building
dressing room; green room; backstage
teahouse; (Edo period) rest stop
butcher's shop; butcher; meat shop
florist; flower shop
wholesale store; wholesale dealer; wholesaler
liquor store; wine shop; bottle shop
barbershop; barber shop; barber
mountain hut (esp. one that offers lodging to climbers and hikers); mountain cottage; mountain shanty
pawnshop
inn
secondhand bookshop; secondhand bookstore; secondhand bookseller
tenement house; row house
barn (for storage); shed; outbuilding
greengrocer; fruit and vegetable shop
fish market; fish dealer; fishmonger
company office building
cavern; grotto
dyer
public bathhouse
confectionery shop; candy store; sweet shop
bakery; baker
real estate agent; realtor
obstinate person; blockhead
general (civil engineering and construction) contractor
restaurant
extortionist that threatens to disrupt stock-holder meetings; sokaiya
playhouse; theatre; theater
confectionery shop; candy store; sweet shop
soba restaurant
shoe store; shoe shop; shoemaker
small-time candy store; penny candy store