Learn English – Is the origin of the term “blackleg” racist

Using Google Books, I found several instances of multi-task in print prior to 1966. Here's the earliest I found, in a description of a lawn mower from a 1954 issue of Chambers's Journal:

Last month a multi-task appliance for turf maintenance was described here, but it was pointed out that its size and cost made it more suitable for use on large areas of grass—e.g. sports grounds, parkland, etc.

I believe this shows that the term multi-tasking did not orginate specifically as computer jargon, but was present prior as engineering jargon.

This earlier use probably did not carry the meaning of performing multiple tasks at the same time, but rather meant, simply, able to perform multiple tasks.

Hit Points as a way of referencing the general remaining health of a person is taken from the game Dungeons and Dragons, originally published back in the '70s. It was the first really popular stat-based role-playing game, and became kind of a touchstone for geekyness.

The idea was that you had a given number of hit points, based on your character class, constitution, and level. When attacked, you lose a certain number based on the power of the attack and a die roll. When/if your "HP" drops to 0, you die.

There are other games that use a "hit point" system these days, and probably were before D&D, but that is the game that popularized the concept. If you hear someone talking about "hit points" in real life, they are making a nerdy D&D reference.