jian2 has two components . The first component is a non-character that in itself denotes 'some form of difficulty'. The second component is gen which means 'root' or 'mountain'. Put together we have the idea 'to till a mountain side which is difficult'.
jian2ju4 means 'herculean task' and literally translates as 'toil'-'huge'.
ju4 is was originally a hieroglyph of a large carpenter's square.
jian2shen1 means 'abstruse' and literally translates as 'toil'-'deep'.
has two components .
The first component denotes 'water' and the second component is a non-character
that originally meant 'chimney' and was extended to mean 'difficult to
reach'. It 'chimney' meaning came about from
meaning 'hole above wood that is burning'. Here we use the extended meaning
of 'hard to reach' combined with the first component of 'water' denotes
'difficult to reach depths' i.e. 'deep'.