box (archaic)
函 centers on a container that holds or encloses something, specifically an archaic box. The idea is of a receptacle that receives and stores items.
函 originally depicted an arrow container or quiver, with the outer 凵 representing the receptacle and the inner part the arrows. Over time it generalized to mean any box or container.
The outer 凵 looks like an open box, and the inner strokes resemble items being placed inside. Picture an old-fashioned box receiving objects: 函 is a box.
For カン, imagine a can that functions as a box: can -> カン, and the can holds things just like the archaic box.
Hakodate (city in Hokkaido)
mailing; posting
posting mail in a postbox or mailbox
armorer; armourer
the Hakone Mountains
drain with an oblong cross-section
box and cover
Hakodate University
Hakodate Line
Hakodate Line Branch Line
homogeneous function
letterbox
caisson
caisson disease; the bends
post office box
sutra box
(cardboard) box manufacture
Seikan Tunnel Memorial Hall Line