Let his posterity
'achariyth  (akh-ar-eeth')
the last or end, hence, the future; also posterity -- (last, latter) end (time), hinder (utter) -most, length, posterity, remnant, residue, reward.
be cut off
karath  (kaw-rath')
to cut (off, down or asunder); by implication, to destroy or consume; specifically, to covenant
and in the generation
dowr  (dore)
a revolution of time, i.e. an age or generation; also a dwelling -- age, evermore, generation, (n-)ever, posterity.
'acher  (akh-air')
hinder; generally, next, other, etc. -- (an-)other man, following, next, strange.
let their name
shem  (shame)
an appellation, as a mark or memorial of individuality; by implication honor, authority, character -- + base, (in-)fame(-ous), named(-d), renown, report.
be blotted out
machah  (maw-khaw')
to stroke or rub; by implication, to erase; also to smooth (as if with oil), i.e. grease or make fat; also to touch, i.e. reach to