[Defiant]

someone could be, saved by the bell or was considered a ...dead ringer.

this part I know is untrue. The form of "dead" used in terms like dead ringer and dead reckoning is not the same as dead as in "not alive". Saved by the bell, I believe, is from boxing.

Some of the other things in this may be true, I don't know.

[Ramius]

The form of "dead" used in terms like dead ringer and dead reckoning is not the same as dead as in "not alive".

If I recall correctly, the "dead" in "dead reckoning" comes from "de'd" which is a shortened form of "deduced". In navigation, it means deducing one's position based on the time, course, and speed from a previous known position.