blackness (Hebrew #6940)

Isaiah
50:3  I clothe
labash (Hebrew #3847)
a primitive root; properly, wrap around, i.e. (by implication) to put on a garment or clothe (oneself, or another), literally or figuratively
KJV usage: (in) apparel, arm, array (self), clothe (self), come upon, put (on, upon), wear.
Pronounce: law-bash'
Origin: or labesh {law-bashe'}
the heavens
shamayim (Hebrew #8064)
from an unused root meaning to be lofty; the sky (as aloft; the dual perhaps alluding to the visible arch in which the clouds move, as well as to the higher ether where the celestial bodies revolve)
KJV usage: air, X astrologer, heaven(-s).
Pronounce: shaw-mah'-yim
Origin: dual of an unused singular shameh {shaw-meh'}
with blackness
qadruwth (Hebrew #6940)
duskiness
KJV usage: blackness.
Pronounce: kad-rooth'
Origin: from 6937
, and I make
suwm (Hebrew #7760)
a primitive root; to put (used in a great variety of applications, literal, figurative, inferentially, and elliptically)
KJV usage: X any wise, appoint, bring, call (a name), care, cast in, change, charge, commit, consider, convey, determine, + disguise, dispose, do, get, give, heap up, hold, impute, lay (down, up), leave, look, make (out), mark, + name, X on, ordain, order, + paint, place, preserve, purpose, put (on), + regard, rehearse, reward, (cause to) set (on, up), shew, + stedfastly, take, X tell, + tread down, ((over-))turn, X wholly, work.
Pronounce: soom
Origin: or siym {seem}
sackcloth
saq (Hebrew #8242)
properly, a mesh (as allowing a liquid to run through), i.e. coarse loose cloth or sacking (used in mourning and for bagging); hence, a bag (for grain, etc.)
KJV usage: sack(-cloth, -clothes).
Pronounce: sak
Origin: from 8264
their covering
kcuwth (Hebrew #3682)
a cover (garment); figuratively, a veiling
KJV usage: covering, raiment, vesture.
Pronounce: kes-ooth'
Origin: from 3680
.