Is there any relationship between 田 (tián), 由 (yóu), 甲 (jiǎ), and 申 (shēn)? Question: Is there any relationship between 田, 由, 甲, and 申?


田 (tián) = field; it seems rarely used
由 (yóu) = ???; I've only seen it as a radical for 油 (yóu) = oil
甲 (jiǎ) = nails, as in fingernails 手指甲 (shǒuzhǐjiǎ); it's also a radical in 鸭子 (yāzi) = duck
申 (shēn) = ???; I've seen it used in 申请 (shēnqǐng) = application


The characters appear similar, so I tend to get them confused often.  It might be there's a reason these characters are similar which might help me remember them better (or there might be no meaningful relationship).
The origin of 田 was a pictograph of a rice field
  
  http://www.zdic.net/z/1e/zy/7530.htm 
  
  The primary meaning of 田 is 'rice field'


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  The origin of 由 was a pictograph of a sprout 
  
  http://www.zdic.net/z/1f/zy/7531.htm 
  
  The primary meaning of 由 is 'from; begin with'


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  The origin of 甲 was a pictograph of the intersection of a planted armor
  
  http://www.zdic.net/z/1f/zy/7532.htm 
  
  The primary meaning of 甲 is 'armor; top class' 


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  The origin of 申 was a pictograph of a man kneeing with pleading hands (to plead to gods)
  
  http://www.zdic.net/z/1f/zy/7533.htm 
  
  The primary meaning of 申 is 'plead'