Bonded by sharing — held together by what both parties give into the space between them.
Modern English coinage (early 20th century, chemistry) from co- (Latin com-, together) + valence (Latin valentia, strength, capacity, from valere, to be strong); bonded by what both parties give into the shared space between them, rather than by one side simply taking.
Bonded by sharing rather than by one side giving in to the other. What holds the bond together is exactly what both parties put into the space between them.