There is no intrinsic or logical connection between the form of specific language signals and the nature of the specific meanings they represent. Instead, the signal and the meaning are linked by either convention or instinct.
Contrasting example: Conveyance of aggression in crabs – strongly threatened crabs express their potential intention to fight by raising their front claw, which is partially iconic given that crabs use their craw pincers to attack prey and defend against predators.