That was a good answer, Leszek, but I think the question was "Why is the
word 'ear' used for this type of inflorescence?" (as opposed to eye or
nose or throat, for example). I confess I do not know the answer to that
question but I do know why the word "corn" is applied to the kernels.
"Corn" used to be descriptive of size (and probably of shape too);
anything the size of a grain of wheat was corn-sized, which is why
wheat is also called "corn" (in the UK). I deduce that the Indian maize
being described as "corn" by the early Europeans was a tad smaller in
the kernel than modern maize. Anyway, this older meaning of the word
"corn" can still be seen in e.g. the name "corned beef"; "corn" here
describes the size of the salt crystals used in the curing -- neither
maize nor wheat have anything to do with it!