Corn means any cereal crop, such as wheat, barley, rye, oats, etc, not necessarily what is called corn in Great Britain.
A. {corn fields}
1] fit for sowing,
2] sown sown fields, growing crops
derivation: from (4703)
http://bible.crosswalk.com/Lexicons/Greek/grk.cgi?number=4702&version=kjv

(4703)
1] a sowing
2] seed (used in sowing)
derivation: from (4687)
http://bible.crosswalk.com/Lexicons/Greek/grk.cgi?number=4703&version=kjv

(4687)
1] to sow, scatter, seed
2] metaphorically, of proverbial sayings
derivation: probably strengthened from (4685) (through the idea of extending)
http://bible.crosswalk.com/Lexicons/Greek/grk.cgi?number=4687&version=kjv

(4685)
1] to draw
2] to draw (one's sword)
http://bible.crosswalk.com/Lexicons/Greek/grk.cgi?number=4685&version=kjv

B. {ear of corn}
1] an ear of corn (except in US) or other growing grain (except corn in US)
derivation: from the base of (2476)
http://bible.crosswalk.com/Lexicons/Greek/grk.cgi?number=4719&version=kjv

(2476)
1] to cause or make to stand, to place, put, set
   1.a] to bid to stand by, [set up]
       1.a.1] in the presence of others, in the midst, before judges, before members of the Sanhedrin;
       1.a.2] to place
       1.b] to make firm, fix establish
           1.b.1] to cause a person or a thing to keep his or its place
           1.b.2] to stand, be kept intact (of family, a kingdom), to escape in safety
           1.b.3] to establish a thing, cause it to stand
2] to uphold or sustain the authority or force of anything
   2.a] to set or place in a balance
       2.a.1] to weigh: money to one (because in very early times before the introduction of
                 coinage, the metals used to be weighed)
3] to stand
   3.a] to stand by or near
       3.a.1] to stop, stand still, to stand immovable, stand firm
   3.b] of the foundation of a building
   3.c] to stand
       3.c.1] continue safe and sound, stand unharmed, to stand ready or prepared
       3.c.2] to be of a steadfast mind
       3.c.3] of quality, one who does not hesitate, does not waiver
http://bible.crosswalk.com/Lexicons/Greek/grk.cgi?number=2476&version=kjv

A link to each occurrence of this word in the homepage:
1] corn
2] corn