Because I knew
da`ath  (dah'-ath)
knowledge -- cunning, (ig-)norantly, know(-ledge), (un-)awares (wittingly).
that thou art obstinate
qasheh  (kaw-sheh')
severe -- churlish, cruel, grievous, hard(-hearted), thing), heavy, + impudent, obstinate, prevailed, rough(-ly), sore, sorrowful, stiff(necked), stubborn, + in trouble.
and thy neck
`oreph  (o-ref')
the nape or back of the neck (as declining); hence, the back generally (whether literal or figurative) -- back (stiff-)neck(-ed).
is an iron
barzel  (bar-zel')
iron (as cutting); by extension, an iron implement -- (ax) head, iron.
giyd  (gheed)
a thong (as compressing); by analogy, a tendon -- sinew.
and thy brow
metsach  (may'-tsakh)
the forehead (as open and prominent) -- brow, forehead, + impudent.
nchuwshah  (nekh-oo-shaw')
copper -- brass, steel.