dead-on

ＳＦのThe Martian by Andy Weirから最後の引用です。
"You ready, Johanssen?" Lewis asked.
"Yes," Johanssen said. "All I have to do is hit enter."
"Martinez, how's our angle?"
"Dead-on, Commander," Martinez reported.
"Strap in," Lewis said.
"dead-on" の意味を辞書で調べます。
・Merriam-Webster: exactly correct or accurate: a dead-on analysis: his impersonations were dead-on
・Dictionary.com: exactly right, accurate, or pertinent: The film director has a dead-on feel for characterization.
語源が気になるので調べました。
Online Etymology Dictionaryの "dead" の語源から抜粋します。
Used from 16c. in adjectival sense of "utter, absolute, quite" (as in dead drunk, first attested 1590s; dead heat, 1796). As an adverb, from late 14c. Dead on is 1889, from marksmanship.
なるほど、射撃で使われ始めた表現なのですね。