walking under the eaves
廡 centers on the space under the eaves of a building, specifically the act of walking or moving within that sheltered area.
廡 combines 广 (building with a roof) with 無, which likely contributes a phonetic element. The character originally referred to a roofed gallery or the space under the eaves.
Under the broad roof 广, there is nothing (無) but open space—perfect for walking under the eaves.
For ブ, imagine walking under the eaves of a grand building while humming a tune: 'boo' -> ブ, as you stroll in the sheltered shade.